8. COSMARIUM, Corda.
Frond simple, constricted in the middle; segments as broad as or broader than long, neither sinuated nor notched.
The fronds are minute, simple, constricted in the middle; the segments are generally broader than long and inflato-compressed, but in some species orbicular or cylindrical; they are neither emarginate at the end nor lobed at the sides, and have no spines or processes.
Ehrenberg united plants belonging to this genus with others having lobed segments, in order to form his genus Euastrum. Meneghini for the most part followed this arrangement, merely changing the name to Cosmarium, which had a prior claim, and also adding some species taken from Xanthidium. Under Micrasterias, Euastrum, and Xanthidium, I have given my reasons for differing from such high
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authorities, and pointed out the characters which distinguish those genera from Cosmarium.
Both Ehrenberg and Meneghini consider the inflato-compressed segments essential; but some species with globular or cylindrical segments can by no means be separated from the compressed ones. Those having cylindrical fronds in some respects show an affinity with Penium; but in that genus the constriction is either wanting or obscure, and the segments are longer than broad. In Cosmarium the fronds are never elongated, are always constricted in the middle, and the starch vesicles are scattered.
Tetmemorus differs from this genus in its elongated fronds and emarginate extremities.
The species belonging to Cosmarium may conveniently be divided into three sections.
In the first section the segments are compressed, and in the front view, which differs from the lateral one, they are united by a portion only of their bases, and thus the constriction forms a linear notch on each side. An end view is elliptic.
The plants belonging to the second section are also compressed, and, like those in the preceding, their front view differs from the lateral one and has a linear notch on each side. Each segment however has a central inflation, which causes the end view to be more or less cruciform.
In the third section the end view is circular, the front and lateral views are alike, and there is no linear notch at the sides, since the segments have no constriction at their junction except that which necessarily results from their figure.
* Frond compressed, deeply constricted at the middle; end view elliptical.
1. C. quadratum (Ralfs); frond smooth, deeply constricted at the middle; segments in the front view quadrate, and on each side of the base slightly protuberant.
Dolgelley, J. R. Rusthall Common near Tunbridge Wells, Mr. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant.
Falaise, Brébisson.
Frond minute, constricted in the middle, the constriction forming a linear notch on each side. The segments are compressed, and in the front view nearly square; on each side of the base there is a slight protuberance.
C. quadratum is smaller than C. Cucumis, and its ends are not so rounded; but as these forms so nearly approach each other, it may prove to be merely a variety. I have however seen no intermediate state, and have therefore kept them distinct.
M. De Brébisson informs me that at the time I described C. quadratum in the 'Annals of Natural History,' he had not only recognized it as distinct, but had conferred on it the same specific name.
Length of frond 1/510 of an inch; breadth 1/952; breadth at constriction from 1/3623 to 1/3472.
Tab. XV. fig. 1. a. front view; b. side view; c. empty frond of variety.
2. C. Cucumis (Corda); frond smooth, deeply constricted at the middle; segments as broad as long and rounded at the end; transverse view broadly elliptic.
Cosmarium Cucumis, Corda, Alm. de Carlsb. 1835, p. 121. f. 27. Meneghini, Synop. Desmid. in Linnaea 1840, p. 220.
Euastrum integerrimum, Ehr. Infus. p. 163. t. 12. f. 9. (1838), according to Meneghini. Kützing, Phycologia Germanica, p. 136 ?
Pithiscus angulosus, Kütz. Phycol. Germ. p. 129 (1845).
Midhurst and Fittleworth, Sussex, Mr. Jenner. Dolgelley and Penzance, J. R. Near Bristol, Mr. Thwaites. Aberdeen, Dr. Dickie. Banffshire, Mr. P. Grant. Ambleside, Mr. Sidebotham.
Germany, Corda, Ehrenberg, Kützing. Falaise, Brébisson. United States, Bailey.
Frond minute, about twice as long as broad, compressed, quite smooth, constricted at the middle, the constriction forming a linear notch on each side. In alpha . the sides are nearly straight, except near the ends, which are rounded; but in beta . the sides also are rounded.
C. Cucumis is smaller than C. Ralfsii; its frond is not so orbicular and the transverse view is different.
Length of frond from 1/362 to 1/257 of an inch; breadth from 1/568 to 1/502; breadth at constriction from 1/1436 to 1/1000.
Tab. XV. fig. 2. a. front view; b. empty frond of var. beta ; c. transverse view.
3. C. Ralfsii (Bréb.); frond orbicular, smooth, deeply constricted at the middle; transverse view fusiform.
Cosmarium Ralfsii, Brébisson in lit. (cum icone) (1846).
Dolgelley, J. R. Bogs at Fisher's Castle near Tunbridge Wells; Fittle-
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worth near Petworth, Sussex; Hampshire, &c., Mr. Jenner. Hill of Rhoil (alt. 1600 feet), Glen Derry, Aberdeenshire, Dr. Dickie. Near Aberdeen, Mr. P. Grant.
Falaise, Brébisson.
Frond large, disciform, quite smooth, deeply constricted at the middle, the constriction forming a linear notch on each side. The segments are semiorbicular, quite entire, and not punctate.
The endochrome is usually somewhat radiate, and the vesicles are small.
The transverse view is elliptico-lanceolate or fusiform.
This species I formerly considered to be the Euastrum integerrimum, Ehr., but M. De Brébisson has convinced me of my mistake. It is a larger plant than that figured by Ehrenberg, and more perfectly orbicular. It differs from C. Cucumis by its larger size and disciform appearance.
Length of frond from 1/227 to 1/222 of an inch; breadth from 1/278 to 1/261; breadth at constriction 1/1250 to 1/1136.
Tab. XV. fig. 3. a. frond with endochrome; b. transverse view.
Probably common. Dolgelley and Penzance, J. R. Barmouth, Rev. T. Salwey. Near Tunbridge Wells; Midhurst; Henfield, &c., Sussex; Reigate, Surrey, Mr. Jenner. Near Congleton, Cheshire, and near Ambleside, Westmoreland, Mr. Sidebotham. Kerry, Mr. Andrews. Hill of Rhoil (alt. 1600 feet), Dr. Dickie. Near Aberdeen, Mr. P. Grant. Near Manchester, Mr. Williamson.
Falaise, Brébisson.
Frond about twice as long as broad, varying much in size, subelliptic, with flattened ends, deeply constricted at the middle, the constriction forming a linear notch on each side.
The empty frond is punctate and entire at the margin. Transverse view broadly elliptic.
The sporangia which I have occasionally met with at Dolgelley are orbicular and tuberculated.
From Cosmarium Cucumis and C. Ralfsii this species may be known by its puncta and depressed ends. From C. ovale, with which I formerly united it, it differs in its entire margin and truncated ends. In form the segments approach those of C. Botrytis, but are not granulate.
Length of frond from 1/471 to 1/264 of an inch; breadth from 1/759 to 1/374; breadth at constriction from 1/2355 to 1/1210.
Tab. XV. fig. 4. a, d. fronds with endochrome; b. empty frond; c, e. lateral views; f. transverse view.
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Cosmarium pyramidatum, Brébisson in lit. (cum icone) (1846).
5. C. tinctum --- ; frond smooth, constriction producing a linear notch on each side; segments elliptic; integument reddish; sporangium naked, subquadrate, conjugating fronds persistent.
Penzance and Dolgelley, J. R. Ashdown Forest and Cross-in-hand, Sussex, Mr. Jenner.
Frond very minute, smooth, smaller than that of Cosmarium bioculatum, deeply constricted at the middle, the constriction causing a linear notch on each side; segments elliptic, twice as broad as long, entire. The empty frond is tinged faint red or straw-colour.
The sporangium is large in proportion to the fronds, and quadrate, with an empty segment of the fronds permanently attached to each corner. Sometimes the fronds couple in a crossed position, when the sporangium appears variously twisted or distorted.
I overlooked this species until I gathered its sporangia near Penzance; and indeed in the growing state it is difficult to distinguish it from Cosmarium bioculatumbut it is rather smaller, the notches formed by the constriction are less gaping, and the empty fronds are slightly coloured. The sporangium however differs not only from that of C. bioculatum, but from all that I have seen.
Length of frond 1/2325 of an inch; breadth 1/2500; length of sporangium 1/1602.
Tab. XXXII. fig. 7. a. front view of frond; b. empty frond; c. side view; d. transverse view; e, f. conjugating fronds; g, h, i. sporangia.
6. C. bioculatum (Bréb.); frond smooth, constriction producing a gaping notch on each side; segments subelliptic, entire; sporangium orbicular, spinous.
Probably common. Tunbridge Wells, Henfield, &c., Sussex, Mr. Jenner. Dolgelley and Penzance, J. R. Near Bristol, Mr. Thwaites. Near Aberdeen, Dr. Dickie and Mr. P. Grant. Ambleside, Westmoreland, Mr. Sidebotham. Rochdale, Mr. Coates.
Falaise, Brébisson. United States, Bailey.
Frond very minute, about as long as broad, deeply constricted at the middle. The segments, which are elliptic, are connected by a more distinct isthmus than in the allied species, hence there is a wider notch on each side. The endochrome is usually more dense in the centre of each segment. The empty frond is not punctate.
The sporangium is orbicular and minute and has conical spines.
Cosmarium bioculatum differs from C. Phaseolus, Bréb. in its smaller size and more elliptic segments, which are not in apposition.
Length of frond 1/1416 of an inch; breadth of segment 1/1773; breadth at constriction 1/5952.
Tab. XV fig. 5. a, b. front view of fronds; c. empty frond; d. transverse view; e, f. sporangia.
7. C. granatum (Bréb.); constriction of frond forming a linear notch on each side; segments compressed, smooth, truncato-triangular.
Cosmarium granatum, Brébisson in lit. cum icone (1846).
Dolgelley and Penzance, very rare, J. R. Bristol, Mr. Thwaites.
Falaise, Brébisson.
Frond rather larger than those of Cosmarium bioculatum and C. Meneghinii, twice as long as broad, deeply constricted at the middle, the constriction forming a linear notch on each side; the segments are quite smooth and entire and slope off rapidly from near the base, so that they would be triangular if the end were not truncate.
Not only were the few fronds that I have seen of this species of a larger size than a figure sent me by M. De Brébisson would indicate, but their segments tapered more rapidly. I have seen neither the transverse nor the end view.
This plant may be identical with Cosmarium Papilio, Meneghini.
Length of frond 1/1234 of an inch; breadth of segment at the base 1/1602; breadth of segment at the end 1/5319; breadth of frond at constriction 1/6111.
Tab. XXXII. fig. 6. a. mature frond; b. empty frond.
††
8. C Meneghinii (Bréb.); frond smooth, deeply constricted at the middle; segments subquadrate, sides and end bicrenate.
Ambleside, Westmoreland, Mr. Sidebotham. Hadlow Down near Mayfield; Henfield; West Chiltington near Pulborough, Sussex; Hants, Kent, and Surrey, Mr. Jenner. Dolgelley, J. R.
Falaise, Brébisson. Italy, Meneghini. Germany, Kützing. United States, Bailey.
The frond is exceedingly minute, quite smooth, and constricted at the middle, the constriction causing a linear notch on each side. The segments are nearly quadrate and the sides and end are bicrenate. The transverse view is elliptic.
Length of frond from 1/853 to 1/735 of an inch; breadth from to 1/1250 to 1/1176; breadth at constriction from 1/5555 to 1/3759.
Tab. XV. fig. 6. a. front view; b. empty frond; c. transverse view.
Euastrum bioculatum, Kützing, Phycologia Germ. p. 136 (1845)
Cosmarium Meneghinii, Brébisson in lit. (cum icone) (1846).
9. C. crenatum (Ralfs); frond punctate, deeply constricted at the middle; segments crenate at the margin and flattened at the end; spines of sporangia very short.
Cosmarium crenatum, Ralfs, in Annals of Nat. Hist. v. 14. p. 394. t. 11.
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Common. Weston Bogs near Southampton, and several stations in Sussex, Mr. Jenner. Dolgelley; Penzance, &c., J. R. Hanham near Bristol, with sporangia, Mr. Thwaites. Yate near Bristol, Mr. Broome. Kerry, Mr. Andrews. Near Manchester; and near Ambleside, Mr. Sidebotham. Craigendanoch (alt. 1436 feet), Aberdeenshire, Dr. Dickie. Hill of Fare (alt. 450 feet), and near Aberdeen, and in Banffshire, Mr. P. Grant.
Falaise, Brébisson.
Frond smaller than that of Cosmarium margaritiferum, twice as long as broad, deeply constricted at the middle, the constriction causing a linear notch on each side. Segments compressed, flattened at the end and crenate at the margin, the surface punctate and even. The end view is elliptic.
The sporangia, which have been gathered abundantly at Bristol by Mr. Thwaites, are orbicular and spinous. The spines, which are very short, and in fact not longer than broad, are divided at the apex and swollen at the base.
The depressed ends distinguish this species from the next.
Length of frond 1/474 of an inch; breadth at constriction 1/1185; breadth of segment 1/678; diameter of sporangium 1/856; length of its tubercles 1/5000.
Tab. XV. fig. 7. a. mature frond; b. empty frond; c. sporangium.
10. C. undulatum (Corda); frond deeply constricted at the middle; segments semiorbicular, crenate at the margin; sporangia with elongated spines.
Near Ambleside, Mr. Sidebotham. Stapleton near Bristol, Mr. Thwaites. Dolgelley, J. R. Henfield, &c., Sussex, Mr. Jenner.
Carlsbad, Corda.
Frond compressed, rather larger than that of Cosmarium crenatum, deeply constricted at the middle, the constriction forming a linear notch on each side. The segments are broader than long, crenate or undulate at the margin, the ends rounded. The crenatores are caused by ridges, which are best seen in an end view of the empty frond. The transverse view is elliptic.
Mr. Thwaites has gathered the sporangia near Bristol. They are orbicular, and their spines, which are divided at the apex and swollen at the base, are elongated, and in this respect differ from the last species.
It is not unlikely that some of the habitats given under Cosmarium crenatum may belong to this species, since I had confounded these plants until Mr. Thwaites's discovery of the different sporangia.
Length of frond 1/416 of an inch; breadth of segment 1/571; diameter of sporangium 1/722; length of the spines of the sporangium 1/3472.
Tab. XV. fig. 8. a, b, d. front views; c. empty frond; e. transverse view; f . sporangium.
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††† Frond with pearly granules which give a denticulate appearance to the margin.
11. C. tetraophthalmum (Kütz.); frond deeply constricted at the middle; segments semiorbicular rough with pearly granules which give a crenate appearance to the margin.
Probably common. Penzance; Dolgelley; and near Carmathen, J. R. Sussex; Hants; and Surrey, Mr. Jenner. Near Bristol, Mr. Thwaites. Near Ambleside, Westmoreland, Mr. Sidebotham. Aberdeen, Mr. P. Grant.
Germany, Kützing. Falaise, Brébisson.
Frond compressed, longer than broad, larger than that of Cosmarium margaritiferum, and deeply constricted at the middle, thus acquiring a linear notch on each side. The segments are semiorbicular, or more usually two-thirds of a circle. The pearly granules, by their roundness, produce at the margin a crenate rather than a dentate appearance. The transverse view is broadly elliptic.
Cosmarium tetraophthalmum may be distinguished from C. Ralfsii and C. pyramidatum by its dentated margin, and from C. ovale by its differently-shaped frond and its scattered granules. The pearly granules are, in their form, unlike those of C. Brebissonii. It is a larger plant than C. margaritiferum, and has also a more rounded margin.
Its sporangia have been gathered by Mr. Thwaites; they are large and their spines finally branched.
Length of frond 1/232 of an inch; breadth of segment 1/326; thickness in side view 1/479. diameter of sporangium 1/435; length of spines of sporangium 1/2732.
Tab. XVII. fig. 11. a. front view of mature frond; b. empty frond; c. transverse view.
Tab. XXXIII. fig. 8. sporangium with empty fronds attached.
Cosmarium ovale, Jenner, Fl. of Tunbridge Wells, p. 196 (1845).
Euastrum tetrophthalmum, Kütz. Phy. Germ. p. 136 (1845).
Cosmarium tetraophthalmum, Brébisson in lit. (1846); not of Meneghini according to Brébisson.
12. C. ovale (Ralfs); frond elliptic, deeply constricted at the middle; segments with a marginal band of pearly granules, the disc punctate.
Weston Bogs near Southampton, Mr. Jenner. Ambleside, Westmoreland, Mr. Sidebotham.
West Point, New York, Bailey. Falaise, Brébisson.
Cosmarium ovale, Ralfs, in Annals of Nat. Hist. v. 14. p. 394. t. 11. f. 7.d, e. (1844); Trans. of Bot. Soc. of Edinburgh, v. 2. p. 15. t. 16. Hassall, Brit. Algae, p. 366.
Euastrum carinatum, Ehr. (Professor Bailey in lit. 1846).
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Frond large, oval, twice as long as broad, deeply constricted at the middle; the apposition of the segments for their entire breadth renders the notch on each side linear; the pearly granules are large and confined to the margin, where they form three to six series, the largest and central row producing a dentate appearance; the rest of the frond is merely punctate.
The endochrome of each segment is often longitudinally divided by a pale line. The transverse view is elliptic.
Cosmarium ovale is one of the largest species in the genus; its oval form and its disc devoid of granules sufficiently characterise it.
Length of frond 1/139 of an inch; breadth of segment 1/240; breadth of connecting portion 1/789.
Tab. XV. fig. 9. a. front view of empty frond; b. side view.
13. C. Botrytis (Bory); frond granulate, deeply constricted; segments, in the front view, truncato-triangular; end view elliptic.
Heterocarpella Botrytis, Bory, Dict. Class. t. 8 (1825).
Cosmarium deltoides, Corda, Alm. de Carlsb. 1835. p. 120. f. 18.
Euastrum Botrytis, Ehr. Infus. p. 163 (1838). Kütz. Phy. Germ. p. 136.
Euastrum angulosum, Ehr. Infus. t. 10. f. 8 (1838).
Cosmarium Botrytis, Meneghini, Synop. Desm. in Linnaea 1840, p. 220. Ralfs, in Annals of Nat. Hist. v. 14. p. 393. t. 11. f. 5; Trans. of Bot. Soc. of Edinburgh, v. 2. p. 15. t. 16. Hassall, Brit. Alg. p. 363.
Euastrum interstitiale, Kützing, Phycologia Germanica, p. 136 (1845), according to Kützing in lit.
Dolgelley and Penzance, J. R. Bristol, Mr. Thwaites. Bexhill, &c., Sussex, Mr. Jenner. Manchester; and Ambleside, Mr. Sidebotham. Essex, Mr. Hassall. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Banffshire, Mr. P. Grant.
Germany, Ehrenberg. Falaise, Brébisson.
Frond compressed, more or less rough with pearly granules, which give a denticulate appearance to the margin, deeply constricted at the middle, the constriction forming a linear notch on each side. In the front view the segments are broadest at the base and gradually narrower towards the end, which is truncated; hence their figure is somewhat angular. The transverse view is elliptic.
The pearly granules are sometimes very evident, sometimes obscure, but they can always be detected at the margin by the higher powers of the microscope.
Mr. Thwaites has gathered a single sporangium near Bristol; it was orbicular its spines elongated and slightly divided at the apex.
Cosmarium Botrytis may be known from C. margaritiferum by its truncate ends; and from C. pyramidatum by its more triangular segments and denticulate margins.
Length of frond from 1/469 to 1/327 of an inch; breadth at constriction 1/2500 to 1/1196; breadth of segment 1/625 to 1/419; diameter of sporangium 1/379; length of spines of sporangium 1/1852.
Tab. XVI. fig. 1. a. mature frond; b. empty frond; c. transverse view;d. sporangium with empty fronds attached.
14. C. margaritiferum (Turp.); frond rough with pearly granules, which are as broad as long; segments semiorbicular or reniform; end view elliptic.
beta. reniformis; segments reniform.
Ursinella margaritifera, Turp. Dict. des Sc. Nat. f. 23 (1820); Mém. du Mus. p. 295. t. 13. f. 19.
Cymbella reniformis, Ag. Consp. Diatom. p. 10 (1830). Leibl. Fl. 1830, p. 315. t. 1. f. 2. Greville, in Hook. Br. Fl. v. 2. p. 415. Harvey, Brit. Alg. p. 215.
Heterocarpella Ursinella, Kützing, Synop. Diatom. in Linnaea 1833, p. 598.
Euastrum margaritiferum, Ehr. Abh. der Berl. Ak. 1833, p. 246; Infus. p. 163. t. 12. f. 7. Kützing, Phycol. Germ. p. 136. Bailey, Amer. Journ. of Science and Arts, v. 41. p. 295. f. 8.
Micrasterias margaritifera, Brébisson, Alg. Fal. p. 55. t. 7 (1835).
Cosmarium margaritiferum, Meneghini, Synop. Desmid. in Linnaea 1840, p. 219. Ralfs, in Annals of Nat. Hist. v. 14. p. 393. t. 11. f. 4; Trans. of Bot. Soc. of Edinburgh, v. 2. p. 15. t. 16.
Very common. Dolgelley; Carnarvon; near Carmarthen; Penzance, &c., J. R. Barmouth, Rev. T. Salwey. Sussex; Kent; Surrey; and Weston Bogs near Southampton, Mr. Jenner. Farnham, Surrey, Mr. Reeves. Herts, Mr. Hassall. Near Bristol, Mr. Thwaites and Mr. Broome. Kerry, Mr. Andrews. Near Manchester, Mr. Gray. Cheshire and Westmoreland, Mr. Sidebotham. Aberdeenshire and Banffshire, Dr. Dickie and Mr. P. Grant. Rochdale, Mr. Coates.
Germany, Leiblein, Ehrenberg and Kützing. Falaise, Brébisson. West Point, New York; and in Mexico, Bailey.
Frond compressed, deeply constricted at the middle, the constriction causing a linear notch on each side. The segments are broader than long, semiorbicular or reniform, and rough with pearly granules, which are as broad as long, and give a dentate appearance to the outline. The transverse view is elliptic.
The sporangia of this species, which I have gathered at Dolgelley, are orbicular and inclosed in a granulate cell, which is usually somewhat angular.
Cosmarium margaritiferum varies in size and form. The rough frond distinguishes it from C. crenatum and C. undulatum; its rounded ends from C. Botrytis; its smaller size and shorter granules from C. Brebissonii, and its less angular shape from C. conspersum.
Length of frond from 1/566 to 1/306 of an inch; breadth from 1/694 to 1/416; diameter of sporangium 1/517; length of spines of the sporangium 1/2293; length of swollen base of spine 1/4629.
Tab. XVI. fig. 2. a. var. beta
; b. empty frond of alpha
; c. transverse view; d. sporangium with empty segments of conjugated fronds. Tab. XXXIII. fig. 3. a, b. mature sporangia.
15. C. Brebissonii (Menegh.); frond rough with conic spines or granules; segments semiorbicular; end view elliptic.
Cosmarium Brebissonii, Meneghini, Synop. Desmid. in Linnaea 1840, p. 219.
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Piltdown Common; Midhurst; Ashdown Forest, near Tunbridge Wells, &c.; Hampshire; Reigate, Surrey, Mr. Jenner. Dolgelley, J. R.
Falaise, Brébisson.
Frond compressed, larger than that of Cosmarium margaritiferum, deeply constricted at the middle, the constriction producing a linear notch on each side. Segments rather broader than long, semiorbicular, rough with pearly granules or spines, which are longer than broad. The transverse view is elliptic.
I am not sure that this form is sufficiently distinct from Cosmarium margaritiferum, as the specific difference chiefly depends on the elongated pearly granules, a character which I fear is inconstant.
Our specimens do not agree exactly with a drawing sent me by M. De Brébisson; but in specimens received from him the spines are less crowded than in his figure. He informs me that " Le Cos. Brébissonii est plus globuleux que le C. margaritiferum, et hérissé de papilles inégales plutôt que de tubercules *."
Length of frond 1/285 of an inch; breadth of segment 1/460; length of marginal spine 1/7353.
Tab. XVI. fig. 3. a. empty frond; b. side view.
16. C. conspersum --- ; frond rough with depressed granules; segments quadrilateral; end view elliptic.
Dolgelley, J. R. Henfield, Mr. Jenner.
Frond compressed, larger than that of Cosmarium margaritiferum and having at the middle a deep constriction, which makes a linear notch on each side; segments rather broader than long, quadrilateral, rough with pearly granules, which give a dentate appearance to the outline. The transverse view is elliptic.
Cosmarium conspersum differs from C. margaritiferum and C. Brébissonii in its quadrilateral figure and in having its granules (which are more depressed than those of C. Brébissonii) arranged in lines. In the front view its form is not unlike some states of C. biretum; but in that species the granules are smaller, and the end margin is more prominent and generally flattened at the centre.
I formerly considered this plant to be the C. Brébissonii, with Meneghini's description of which it certainly agrees better than a specimen so named which has been sent me by M. De Brébisson.
Length of frond 1/262 of an inch; breadth at constriction 1/961; breadth of segment 1/357.
Tab. XVI. fig. 4. a. empty frond; b. transverse view.
* I add Meneghini's characters of the two species: ---
" C. margaritiferum, cellulis e dorso ellipticis, e latere semiorbicularibus, superficie granulato-margaritifera."
" C. Brébissonii; cellulis e dorso elongato-ellipticis, e latere introrsum curvatis, formam trapezii prae se ferentibus, superficie granulato-margaritacea."
17. C. amoenum (Bréb.); frond twice as long as broad, with parallel sides and rounded ends, deeply constricted at the middle, rough with pearly granules.
Ambleside, Westmoreland, Mr. Sidebotham. Dolgelley, J. R.
Falaise, Brébisson.
Frond smaller than that of Cosmarium margaritiferum, twice as long as broad, deeply constricted at the middle, the constriction causing a linear notch on each side; the sides nearly straight and the ends rounded. Segments campanulate, rough with crowded, obtuse, papilla-like, pearly granules which give a dentate appearance to the margin. The side view is narrower and about thrice as long as broad.
In form, Cosmarium amoenum resembles the cylindrical species rather than the compressed ones with which it is here classed; but its smaller size and nearly parallel sides will distinguish it from the other species of the latter, whilst from the former it may be known, in the front view, by the linear notch which the constriction produces on each side.
Length of frond 1/568 of an inch; breadth at constriction 1/1470; breadth of segment 1/1141.
Tab. XVII. fig. 3. a. mature frond; b. empty frond; c. side view.
** Constriction, in the front view, forming a linear notch on each side; end view with a lobe or protuberance on each side.
†
18. C. biretum (Bréb.); segments compressed, quadrilateral, broadest at the end; the end margin convex, slightly truncate at the middle; end view with a lobe on each side.
Hastings and Bexhill, Sussex, Mr. Jenner.
Falaise, Brébisson.
Frond larger than that of any other species in this section, deeply constricted at the middle, the constriction forming a linear notch on each side. The segments are compressed, quadrilateral or somewhat hexagonal, nearly twice as broad as long, narrowest at the base and gradually dilated upwards. The end margin, which is the longest, is more convex in Sussex than in French specimens, and becomes angular from being slightly flattened at the middle.
The empty frond appears punctate rather than granulate.
An end view is slightly inflated at the middle. The inflation in this and the two following species depends upon a central protuberance of the segment, similar to that observable in some species of Xanthidium, and in this respect
differs from the inflation of Cosmarium ornatum and C. commissurale, in which plants it is longitudinal, and extends to or beyond the end margin.
From all except Cosmarium Broomeii, this species is known by its quadrangular segments, the lateral margins of which are sloped, not rounded. From that species it differs in its larger size, more distinct angles, and the greater comparative length of the end margin, which is also convex and slightly angular, whilst in C. Broomeii it is nearly straight.
Length of frond 1/333 of an inch; breadth at constriction 1/1376; breadth of segment 1/372.
Tab. XVI. fig. 5. a. Sussex specimen; b. empty frond of French specimen; c. end view.
19. C. Broomeii (Thwaites); segments compressed, minutely granulate, quadrilateral; end view slightly inflated at the middle.
In brackish water at Shirehampton near Bristol, Mr. Broome and Mr. Thwaites. Piltdown, Sussex, Mr. Jenner.
Frond as large as that of Cosmarium margaritiferum, deeply constricted at the middle, the constriction forming a linear notch on each side. The segments are compressed, minutely granulate, quadrilateral, and twice as broad as long; the end margin is straight.
The end view is twice as long as broad, slightly inflated at the middle and broadly rounded at the ends. In the transverse view the inflation is greater, and there is a slight constriction between it and the ends.
Cosmarium Broomeii resembles in the front view some states of C. margaritiferum, but differs in the end one. The inflation does not project at the margin in the front view, as in C. ornatum, and the lateral margins are less rounded, the pearly granules, are also smaller.
Length of frond 1/500 of an inch; greatest breadth 1/540; breadth at constriction 1/1562; thickness at the inflation in end view 1/930; least thickness in the end view 1/1157. Diameter of sporangium 1/548.
Tab. XVI. fig. 6. a. frond with endochrome; b. empty frond; c. end view; d. transverse view.
Tab. XXXIII. fig. 7. sporangium.
20. C. caelatum --- ; frond suborbicular; segments crenate, rough with pearly granules; end view slightly inflated at the middle.
Near Machynlleth, North Wales, J. R. Tunbridge Wells and Ashdown Forest, Sussex, Mr. Jenner.
Falaise, Brébisson.
Frond nearly orbicular, scarcely so large as that of Cosmarium margaritiferum, compressed, constricted at the middle, the constriction causing a linear notch on each side. The segments are scolloped or broadly crenate: each segment has six crenatures, four at the end, one at each side and one at each intermediate angle, the lateral ones being the largest, whilst between all the
crenatures the margin is somewhat sulcated. The pearly granules are distinct, especially on the crenatures, to which they give a dentate appearance. The end view is slightly cruciform, and the transverse view still more so. The lateral view is constricted at the middle and emarginate at the ends.
Cosmarium caelatum is a very distinct species and requires no comparison with any other.
Length of frond from 1/921 to 1/581 of an inch; greatest breadth from 1/1024 to 1/608; breadth at constriction from 1/2137 1/1538.
Tab. XVII. fig. 1. a. frond with endochrome; b. empty frond; c. empty frond of Sussex specimen; d. dividing frond; e. side view; f. end view. g. transverse view.
21. C. ornatum ( Ralfs); segments twice as long as broad, rough with pearly granules which give a dentate appearance to the margin; inflation forming a truncate projection at the end ; end view cruciform.
Cosmarium ornatum, Ralfs in Annals of Nat. Hist. v. 14. p. 392. t. 11. f. 3 (1844). Trans of Bot. Soc. of Edinburgh, v. 2. p. 148. t. 16. Jenner, Fl. of Tunbridge Wells, p. 194. Hassall, Br. Alg. p. 364.
Cosmarium Sportella, Brébisson, MS.
Not uncommon. Dolgelley; Barmouth; and Penzance, J. R. Ashdown Forest, &c., Sussex, and Weston Bogs near Southampton, Mr. Jenner. Cheshunt, Mr. Hassall. Kerry, Mr. Andrews. Ben Muich Dhu (alt. 2800 ft.); Linn of Dee (1190 ft.); Little Craigendall, Braemar Aberdeenshire, Dr. Dickie. Aberdeen, Mr. P. Grant. Ambleside, Westmoreland, Mr. Sidebotham.
Falaise, Brébisson. West Point, New York, Bailey.
The frond is generally smaller than that of Cosmarium margaritiferum and deeply constricted at the middle ; the constriction forms on each side a linear notch, which is nearly closed by the apposition of the segments. The segments are compressed, about twice as broad as long, and rough with pearly granules which give a dentate appearance to the margin. The inflation extends beyond the margin in a truncate projection, and in the end view forms a rounded lobe on each side, producing a cruciform figure.
Cosmarium ornatum differs from the other species by its inflation extending into a truncate projection beyond the margin.
The sporangium has been found near Bristol by Mr. Broome, and I have gathered it at Penzance. Its spines are elongated, slightly divided at the extremity and dilated at the base.
Length of frond 1/613 of an inch; greatest breadth 1/613; breadth at constriction 1/2041; diameter of sporangium; length of spine of sporangium 1/1582.
Tab. XVI. fig. 7. a. front view of mature frond ; b. empty frond; c. end view; d. transverse view; e. sporangium.
22. C. commissurale (Bréb.); segments narrow-reniform, three times broader than long, rough with pearly granules; end view with a constriction between the central infation and the extremities.
Piltdown Common, Sussex, Mr. Jenner. Near Penzance, J. R. Near Bristol, Mr. Thwaites.
Falaise, Brébisson.
Frond smaller than that of any other species in this section, broader than long, very deeply constricted at the middle. The segments are compressed, three times as broad as long, reniform, sometimes inclining to triangular in consequence of the projection of the inflation at the margin; they are rough with pearly granules which give a dentate appearance to the outline. The transverse view is three times longer than broad, with a constriction between the central inflation and the rounded ends.
The sporangia have been gathered very sparingly by Mr. Jenner. They are orbicular, with slender, elongated spines, which are slightly divided at the apex and dilated at the base.
The great breadth of the frond compared with its length and the reniform segments well distinguish this species.
Length of frond 1/923 of an inch; greatest breadth 1/663 to 1/609; breadth at constriction 1/2155; thickness of central inflation in end view 1/1147; diameter of sporangium 1/721; length of spine of sporangium 1/1256.
Tab. XVI. fig. 8. a. front view of frond; b. empty frond; c. transverse view; d. sporangium.
23. C. cristatum --- ; frond orbicular, deeply constricted at the middle, margined by papilla-like pearly granules; end view linear, with an inflation at the middle of each side.
Ambleside, Westmoreland, Mr. Sidebotham.
Frond exactly orbicular, much compressed, deeply constricted at the middle, the constriction forming a linear notch on each side; the segments margined by a series of obtuse, papilla-like, pearly granules. At the centre of each segment is a circular granulate inflation. The end view is nearly linear, with truncate ends and an inflation on each side at the middle. The above description is founded on Mr. Jenner's notes and drawings. I have not seen this plant, but have no doubt that it is a good species.
Length of frond 1/699 of an inch; greatest breadth 1/653; breadth at constriction 1/1785,
Tab. XVII. fig. 2. a. front view of mature frond; b. empty frond ; c. end view.
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24. C. Phaseolus (Bréb.); segments smooth, reniform; constriction forming a linear notch on each side; end view elliptic with a slight projection at the middle of each side.
Cosmarium Phaseolus, Brébisson, in Menegh. Synop. Desmid. in Linnaea 1840, p. 220. Brébisson, in lit. cum icone.
Dolgelley and Penzance, J. R.
Falaise, Brébisson.
Frond larger than that of Cosmarium bioculatum, deeply constricted at the middle, the constriction forming a linear notch on each side; segments twice as broad as long, reniform, quite smooth and entire. The end view is elliptic and shows on each side a slight conical inflation, resembling that seen in Xanthidium fasciculatum.
The small circular inflation which is present at the centre of each segment compels me to associate this with the other inflated species; but it differs from all of them in its smooth fronds, and the slight inflation can be detected only by an end view. Cosmarium Phaseolus is far more likely to be mistaken for C. bioculatum, and indeed is placed next it by Brébisson; but it is larger, its segments are reniform, not elliptic, and the notches caused by the constriction are not gaping as in that species.
Length of frond 1/787 of an inch; breadth 1/833; breadth at constriction 1/3048.
Tab. XXXII. fig. 5. a. front view; b. empty frond; c. end view.
*** Constriction not forming linear notches at the sides; end view circular.
† Frond rough with pearly granules which give a denticulate appearance to the outline.
25. C. cylindricum (Ralfs); segments granulated, subquadrate in the front view, broadest at the extremity; end view circular.
Wet sides of a cave at Lamorna Cove near Penzance, and wet sides of a cliff at Machynlleth, North Wales, J. R. Ashdown Forest; near Tunbridge
Wells, and near Battle, Mr. Jenner.
Frond minute, cylindrical, about twice as long as broad. The subquadrate segments are broadest at the extremity, which is truncate, somewhat tapering towards the junction, and rough with pearly granules which give a dentate appearance to the outline.
Cosmarium cylindricum may be known from C. Cucurbita by the condition of its segments described above.
Length of frond 1/588 of an inch; greatest breadth 1/1060; breadth at constriction 1/1678.
Tab. XVII. fig. 4. a. mature frond; b. empty frond; c. end view.
26. C. orbiculatum (Ralfs); segments spherical, rough with pearly granules.
Cosmarium orbiculatum, Ralfs, Ann. of Nat. Hist. v. 14. p. 392. t. 11. f. 2 (1844); Trans. of Bot. Soc. of Edinburgh, v. 2. p. 148. t. 16. Hass. Br. Alg. p. 364.
Dolgelley, J. R. Midhurst, Sussex, Mr. Jenner. Ambleside, Westmoreland, Mr. Sidebotham.
Falaise, Brébisson.
Frond minute, composed of two spherical segments, rough with pearly granules, giving a dentate appearance to their outlines, but wanting on the necklike contraction between them. The transverse view has a large central opening.
Cosmarium orbiculatum varies in size; the larger specimens somewhat resemble the lateral view of Cosmarium margaritiferum; the front view however of that species differs in the shape of the segments and in the presence of a linear notch on each side at their junction. The granulated fronds distinguish it from the following species; its central opening also is much larger.
Length of frond from 1/498 to 1/454 of an inch; greatest breadth from 1/757 to 1/748; breadth at constriction 1/1219; diameter of sporangium 1/383; length of spine 1/2500.
Tab. XVII. fig. 5. a. mature frond; b. empty frond; c. transverse view.
Tab. XXXIII. fig. 9. sporangium.
27. C. moniliforme (Turp.); segments spherical, smooth.
alpha. Segments united without the intervention of a neck.
beta. Segments united by a distinct neck.
Tessarthronia moniliformis, Turp. Dict. des Sc. Nat. t. 7. f. 1. ? (1820).
alpha . Dolgelley; rare; J. R. Charlton Fields near Manchester, Mr. Sidebotham. Ashdown Forest; Fittleworth; and Rackham Bogs near Pulborough, Sussex, Mr. Jenner.
beta. Penzance.
The frond is small and quite smooth. In alpha. each segment is a perfect globe, having a very small opening through which it connects with its fellow. Their appearance is one of mere juxtaposition, and their junction can only be ascertained and the opening seen in a transverse view. This state is liable to be mistaken for a not uncommon plant with two globular cells, which I consider to belong properly to the Palmelleae, and to be the Scenedesmus moniliformis of Kützing's , Phycologia Germanica' and Brébisson´s 'Alg. Fal.,' as also the Trochiscia moniliformis of Meneghini's , Synopsis Desmidiearum.' The resemblance indeed is at times so complete that I have occasionally been puzzled to distinguish them; but in specimens of the latter some individuals may gene-
Tessarthra moniliformis, Ehr. Abh. d. Berl. Ak. 1835, p. 173; Infus. p. 145. t. 10. f. 20.
rally be perceived which have a slight interval between the globes, whilst its solitary globes are filled with endochrome. In Cosmarium moniliforme, as the globes are united they are in close contact, and when separated their contents escape at the orifice.
Both Kützing and Meneghini refer to the Tessarthra moniliformis as identical with the plant described by them under the names mentioned above, but I have no hesitation in considering that it is the present plant. Ehrenberg's figure, which exhibits a frond dividing and forming two smaller globes between the original ones, appears to me decisive of the question. M. De Brébisson concurs in this opinion, that the Tessarthra moniliformis, Ehr., is not the Trochiscia moniliformis of Meneghini's 'Synopsis.'
The var. beta. resembles more nearly the form of Cosmarium orbiculatum, from having, like that species, a distinct connecting neck; but its fronds are quite smooth and without granules or puncta.
Length of frond 1/617 of an inch; greatest breadth 1/1131; breadth at constriction 1/2500.
Tab. XVII. fig. 6. a. usual state; b. variety beta; c, d. dividing fronds; e. empty frond; f . transverse view.
28. C. connatum (Bréb.); segments punctate, each about two-thirds of a circle, uniting by their plane surfaces; end view circular.
Ambleside, Westmoreland, Mr. Sidebotham. Dolgelley, J. R.
Falaise, Brébisson.
This is one of the largest species in the genus. The fronds are nearly twice as long as broad, and slightly constricted at the middle. In the front view the segments are broader than long; one-third of the margin is interrupted by their broad junction, and the remainder constitutes two-thirds of a circle; a distinct border is always present, and often appears striated.
The empty frond is punctate rather than granulate, and the end view is circular.
With a little attention this species is easily recognized. Its very broad junction without lateral incisions distinguishes it from those species which have compressed fronds, and its large size and segments broader than long from those which have a circular end view. Its aspect in the front view is more like that of Staurastrum tumidum, but the latter has more elliptic segments,
and generally shows one at least of its nipple-like angles.
Length of frond 1/285 of an inch; greatest breadth 1/1155; breadth at con-
striction 1/1479.
Tab. XVII. fig. 10. a. mature frond; b. empty frond.
29. C. Cucurbita (Bréb.); frond punctate, slightly constricted at the middle and rounded at the ends; transverse view circular.
Cosmarium Cucurbita, Bréb. in Desm. Alg. No. 1103 (184 ). Ralfs, Annals of Nat. Hist. v. 14. p. 395. t. 11. f. 10; Trans. of Bot. Soc. of Edinb.
v. 2. p. 151. t. 16. Jenner, Fl. of Tunbridge Wells, p. 196. Hass. Br. Alg. p. 367.
Rather common. Dolgelley; near Lampeter; and Penzance, J. R. Ashdown Forest, Greatham Bogs near Pulborough, Sussex; and near Southampton, Mr. Jenner. Near Bristol, Mr. Thwaites. Near Congleton, Cheshire; and Ambleside, Westmoreland, Mr. Sidebotham. Kerry, Mr. Andrews.
Falaise, Brébisson. Germany, Kützing.
The frond is minute, subcylindrical, twice as long as broad, with a very slight constriction at the middle, and rounded at the ends. The transverse view is circular, with a large opening.
Cosmarium Cucurbita agrees in size with C. cylindricum, but is punctate, not granulate. The segments differ also in figure from those of that plant, and resembling two cupping-glasses with their mouths in contact, are aptly characterized by the specific name.
Length of frond 1/586 of an inch; greatest breadth 1/1155; breadth at constriction 1/1479.
Tab. XVII. fig. 7. a. front view of mature frond; b, c. empty fronds; d. transverse view; e. dividing frond.
30. C. Thwaitesii --- ; frond cylindrical, constricted at the middle and rounded at the ends; puncta very indistinct.
Closterium clandestinum, Kütz. Phy. Germ. p. 132 (1845). (Kützing in lit.)
Bristol, Mr. Thwaites. Swansea, J. R.
Frond two to three times longer than broad, larger than that of Cosmarium Cucurbita, which in form this species much resembles; sides parallel, the middle slightly constricted and the ends broadly rounded. Mr. Jenner finds very faint, minute, scattered puncta after the escape of the endochrome. Mr. Thwaites's specimens were very gelatinous, but I was unable to ascertain whether each plant had a distinct mucous covering, or was merely imbedded in a common matrix. The transverse view appears to me cylindrical, but Mr. Jenner finds the segments slightly compressed.
Cosmarium Thwaitesii differs from C. Cucurbita in its larger size and in distinct puncta; from C. curtum in its differently arranged endochrome; and from C. turgidum and C. attenuatum in its nearly parallel sides.
Length of frond 1/357 of an inch; greatest breadth 1/801; breadth at constriction 1/833.
Tab. XVII. fig. 8. a. fronds surrounded with gelatine; b. empty frond; c. transverse view.
31. C. curtum (Bréb.); frond oblong, constricted at the middle and rounded at the ends; endochrome in longitudinal fillets.
Near Bristol, Mr. Thwaites. Penzance, J. R.
Falaise, Brébisson. Germany, Kützing.
Penium curtum, Brébisson, in lit. cum icone (1846).
Frond minute, smooth, two to three times longer than broad, slightly constricted at the middle, attenuated and rounded at the ends. Endochrome in three or four longitudinal fillets, which are interrupted at the suture. End view circular, its endochrome with four geminate rays.
This plant was placed in Penium by M. De Brébisson because its endochrome is arranged in fillets, but in every other respect it agrees better with some of the preceding species of this genus. It is more obtuse than the usual form of Cosmarium attenuatum, but I have occasionally seen specimens of the latter so nearly resembling the figure of C. curtum that I have doubted to which species they belonged. It is much smaller than C. turgidum, and tapers more than C. Cucurbita and C. Thwaitesii.
Length of frond 1/465 of an inch; greatest breadth 1/1064.
Tab. XXXII. fig. 9. a. mature frond; b. empty frond ; c. end view of frond with stellate endochrome.
32. C. attenuatum (Bréb.); frond fusiform, three or four times longer than broad, slightly constricted at the middle; transverse view circular.
Cosmarium attenuatum, Brébisson, in lit. cum icone (1846).
Near Bristol, Mr. Thwaites. Swansea, J. R.
Falaise, Brébisson.
Frond three or four times longer than broad, tapering, its ends obtuse; end view circular. The empty frond is finely punctate.
Cosmarium attenuatum is much smaller and more tapering than C. turgidum, and has less-rounded ends. Its fusiform frond distinguishes it from C. Thwaitesii and C. Cucurbita. In general it tapers more than C. curtum, but sometimes its ends are more obtuse, and then these species can only be distinguished by the different arrangement of their endochromes.
It is doubtful whether this plant and Cosmarium turgidum ought not to be removed to Penium.
Length of frond from 1/420 to 1/416 of an inch; greatest breadth from 1/1068 to 1/1022; breadth at constriction from 1/1142 to 1/1099.
Tab. XVII. a, b. fronds in usual state; c. empty frond; d. transverse view.
33. C. turgidum (Bréb.); frond oblong, punctate, constricted at the middle and rounded at the ends ; transverse view circular.
Henfield, Mr. Jenner. Swansea, J. R.
Falaise, Brébisson.
Frond large, oblong, turgid, about three times as long as broad, distinctly constricted at the middle and broadly rounded at the ends. Empty frond with numerous, minute, scattered puncta.
Cosmarium turgidum differs from the allied species in its much greater size. It is comparatively longer and more tapering than C. Cucurbita and C. Thwaitesii, and its ends are more rounded than those of C. attenuatum.
111
Length of frond 1/126 of an inch; greatest breadth 1/249: breadth at constriction 1/271.
Tab. XXXII. fig. 8. a. mature frond; b. empty frond; c. transverse view.
