7. EUASTRUM, Ehr.
Frond simple, compressed, deeply divided into two segments which are emarginate at their ends, lobed or sinuated, generally pyramidal and furnished with circular inflations.
The fronds are simple, longer than broad, often oblong, compressed, and so deeply constricted that their segments seem only united by a narrow chord. The generally pyramidal segments are broadest at their bases, and are there in such close apposition for their entire breadth as nearly to conceal the notch on each side until the endochrome has collapsed. They are attenuated towards the ends, which in the adult state are almost always more or less emarginate, and their sides are more or less lobed or sinuated. The surface is irregular with inflated prominences, which also form tubercle-like projections along the margins ; their number and situation are, probably, constant in the adult fronds of the same species and different in distinct species. A transverse view is (when the segments are separated) the best method of ascertaining their number; the terminal lobe has similar prominences.
In Euastrum, Ehrenberg includes Micrasterias, Ag. (not Micrasterias, Ehr.) and Cosmarium, and in this he is followed by Kützing in his 'Phycologia Germanica.' Meneghini separates Micrasterias from Euastrum, but includes the latter in Cosmarium. Euastrum appears to me distinct from both, and especially from Cosmarium.
Euastrum agrees with Micrasterias in having lobes and emarginate ends, but the lobes are not incised, nor do they radiate from the centre, and the inflated projections will distinguish it not only from Micrasterias, but from every other genus in the family. From Cosmarium it differs also in the lobed and emarginate segments.
I have divided this genus into three sections. In the first section the fronds are comparatively large, and appear to the naked eye like roundish or oblong dots. The segments are distinctly lobed; the terminal lobe, cuneate and itself emarginate, is partly included in a notch between the projections of the lateral lobes, and the sinuses
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which separate it from them are deep, and directed inwards and downwards.
In the second section the fronds are more minute and scarcely visible to the naked eye; the segments are less decidedly lobed, but the margin is crenate or sinuated, and the terminal portion unites with the basal by a neck-like contraction of the segment, and is therefore never included within a notch; the corners are rounded. The outline of a segment has some resemblance to that of a decanter or water-bottle.
The third section contains those species which do not well agree with those in the preceding ones. The fronds are extremely minute, the segments are generally still less lobed than in the last, and the form of the front view is more irregular and frequently differs in having a process or an acute angle at either the corners or the sides of the terminal portion.
Several species have been observed in a conjugated state.
* Segments of the frond deeply lobed; the terminal lobe cuneate, and partly included in a notch formed by the projection of the lateral lobes.
1. E. verrucosum (Ehr.); frond rough with conic granules; the segments three-lobed; lobes broadly cuneate with a broad shallow notch.
Euastrum verrucosum, Ehr. Abh. d. Berl. Ak. p. 247 (1833); Infus. p. 162. t. 12. f. 5. Ralfs, Annals of Nat. Hist. v. 14. p. 189. t. 6. f. 3; Trans. of Bot Soc. of Edin. v. 2. p. 125. t. 10. Hass. Brit. Alg. p. 379. Kütz. Phycologia Germanica, p. 135.
In pools. Cheshunt, Mr. Hassall. Weston Bogs near Southampton; Rusthall Common and elsewhere near Tunbridge Wells ; Ashdown Forest, Sussex; Hampshire ; and Reigate, Surrey, Mr. Jenner. Penzance and Dolgelley, J. R. Near Ambleside, Westmoreland, Mr. Sidebotham. Aberdeenshire and Banffshire, Mr. P. Grant.
Germany, Ehrenberg, Kützing. Falaise, Brébisson. New York, Bailey.
Frond rather longer than broad, angular; the segments, which slightly diverge from each other, are deeply three-lobed ; the lobes are broad, cuneate, with a broad shallow notch. Surface of the frond furnished with numerous conic granules, which give the margins a dentated appearance, especially the more prominent parts : each segment has two circular prominences near the base; on these the granules form two or three concentric circles with a granule in the centre; the terminal lobe has two similar but smaller prominences.
Cosmarium verrucosum, Menegh. Synop. Desmid. in Linnaea 1844, p. 222.
The side view, which is not so broad as the front one, is inflated at the base, attenuated upwards into a short neck, and emarginate and slightly dilated at the end. A transverse view is oblong, with three inflations at each side and a smaller one at each end. The terminal lobe, as seen by an end view, is four-lobed.
Euastrum verrucosum, when once seen, is not liable to be confounded with any other species, but may be known by the conic granules giving a dentate appearance to the outline.
Length of frond 1/267 of an inch; breadth 1/270.
Tab. XI. fig. 2. a. frond with endochrome; b. empty frond; c. side view; d. end view.
2. E. oblongum (Grev.); frond smooth, oblong; segments five-lobed; lobes cuneate, emarginate, the terminal one partly included between the lateral ones.
Hab. Pools; common. Appin, Capt. Carmichael. Penzance; Dolgelley and Carnarvon, J. R. Warbleton, Henfield, &c., Sussex; Tunbridge Wells; Reigate, Surrey; and Weston Bog near Southampton, Mr. Jenner. Brookhouse Moss, near Congleton, Cheshire, and near Ambleside, Westmoreland, Mr. Sidebotham. Aberdeen, Mr. P. Grant and Dr. Dickie.
Falaise, Brébisson. Germany, Ehrenberg, Kützing. New York; Rhode Island and Virginia, Bailey.
Frond comparatively large, appearing to the naked eye like a small dot, oblong, three or four times longer than broad; each segment divided into five lobes in a pinnatifid manner. The lateral lobes are broad, cuneate, with a broad shallow notch. The terminal lobe is cuneate and its notch linear; the corners of all the lobes are rounded. The empty fronds are punctated.
The transverse view is three times longer than broad, and has three rather distant inflations or lobes on each side (the largest in the centre) and one at each end. I have not seen the end view myself, but Mr. Jenner finds the terminal lobe twice as long as broad, slightly constricted at the middle, its ends notched rather than lobed.
The sporangia are orbicular, and furnished with numerous conical tubercles; they have been met with only near Dolgelley.
The young fronds are smaller and have the middle lobe entire.
Length of frond 1/156 of an inch; breadth 1/282; breadth of end lobe 1/555; diameter of sporangium 1/175; length of tubercle 1/1000.
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Tab. XII.fig. 3. a. mature frond with endochrome; b. empty frond; c. mature frond of small variety; d. transverse view; e. transverse view of small variety; f. end view; g. sporangium.
3. E. crassum (Bréb.); frond smooth; segments three-lobed, subquadrilateral; terminal lobe cuneate, partly included in a notch formed by the lateral lobes.
Euastrum Pelta, Ralfs, in Annals of Nat. Hist. v. 14. p. 190. t. 7. f. 1. (1844), (not Cosm. Pelta, Corda, according to Brébisson); Trans. Bot. Soc. of Edin. p. 126. Hass. Br. Freshwater Algae, p. 380.
Euastrum crassum, Kütz. Phycologia Germ. p. 135 (1845).
Euastrum (No. 5), Bailey, Amer. Bacil. t. 1. f. 26.
beta. Smaller, sides more concave.
Hab. Pools; common. Dolgelley, Penzance, J. R. Weston Bogs near Southampton; Ashdown Forest, Sussex, and Fisher's Castle, Kent, Mr. Jenner. Ambleside, Westmoreland, Mr. Sidebotham. Aberdeen, Mr. P. Grant and Dr. Dickie. Ben Muich Dhu and Glen Lin, Aberdeenshire, Dr. Dickie.
beta. Dolgelley, J. R.
Falaise, Brébisson. United States, Bailey. Germany, Kützing
Frond comparatively large, visible to the naked eye, about three times longer than broad; of a quadrilateral form, with rounded ends; terminal lobe cuneate, partly included between the ends of the lateral lobes, rounded and emarginate, the notch closed ; the segments of the frond are broad, three-lobed, or rather each segment has a subquadrate base and a terminal lobe. The basal portion is not attenuated, and each lateral margin has a broad shallow sinus, in which there is frequently a slight intermediate rounded projection.
The transverse view is two or three times longer than broad, with three lobes on each side and one at each end.
The empty frond is punctated.
The var. beta , regarded by Brébisson as a distinct species, is smaller, the segments have more concave sides, their base is more inflated, and the angles which include the terminal lobe are more elongated.
The E. cornutum, Kütz., differs in having the outer angles of the lateral lobes elongated into processes.
Length of frond from 1/193 to 1/132 of an inch; breadth from 1/263 to 1/260; breadth of end lobe 1/537.
Tab. XI. fig. 3. a. frond with endochrome; b. empty frond; c. transverse view; d. end view; e. frond of beta ; f. end view.
** Segments sinuated; terminal lobe exserted and united with the basal portion by a distinct neck.
4. E.pinnatum, --- ; segments five-lobed; end lobe exserted, dilated; upper margin of lobes horizontal.
Dolgelley, rare, J. R.
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Frond oblong, and rather smaller than that of E. oblongum. Segments deeply five-lobed in a pinnatifid manner ; the terminal lobe is exserted, dilated and emarginate; the basal lobes are emarginate and the intermediate ones smaller and entire; the upper margins of all are horizontal. The transverse view is oblong, with three lobes or projections on each side and one at each end. The empty frond is punctate, and the inflated projections are strongly marked.
Euastrum pinnatum somewhat resembles, but is smaller than E. oblongum; the terminal lobe joins the others with a distinct neck ; the intermediate lobes are always simple and smaller than the basal, and all the sinuses are more rounded. There is more difficulty in separating Euastrum affine; still, when it is compared with E. pinnatum the distinction is easily perceived, for the latter is a larger plant, and is also distinctly five-lobed; but in the former the intermediate lobes resemble tubercles, as the sinuses between them and the basal ones are much shallower.
Length of frond 1/188 of an inch; breadth at basal lobes 1/357; breadth at middle lobes 1/454; breadth at end 1/625; breadth of neck 1/1101.
Tab. XIII. fig. 1. a. frond with endochrome; b. empty frond; c. side view; d. transverse view; e. end view.
5. E. humerosum, --- ; segments with terminal lobe dilated, emarginate; neck partly included between the elongated middle lobes, which resemble processes; basal lobes emarginate.
Frond smooth, two or three times longer than broad; segments sub-five-lobed; the basal lobes are emarginate; the terminal one is dilated, its notch linear and the neck is short and partly included between the elongated processes or tubercles which represent the middle lobes. The transverse view has three lobes on each side and one at each end. The empty frond is minutely dotted.
Euastrum humerosum corresponds in size with E. affine, of which I formerly considered it a variety, but Mr. Jenner finds that they differ essentially in the transverse view. The present species is distinguished from all in this section by its included neck.
Length of frond 1/225 of an inch; breadth of segment at base 1/382; breadth at end 1/727; breadth of neck 1/1199; length of projections at side of neck 1/2314.
Tab. XIII. fig. 2. a. frond with endochrome; b. empty frond; c. transverse view.
6. E. affine (Ralfs); segments three-lobed, with intermediate tubercles; lobes emarginate, the end one dilated, its notch linear.
Euastrum affine, Ralfs, Annals of Nat. Hist. v. 14. p. 191. t. 7. f. 3. (1844); Trans. of Bot. Soc. of. Edin. v. 2. p. 128. Hass. Brit. Alg. p. 382.
Dolgelley, J. R. Ambleside, Mr. Sidebotham. Sussex and Hampshire, Mr. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant.
Falaise, France, Brébisson.
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Frond about three times as long as broad; segments pyramidal, three-lobed, and having on each side a tubercle, which replaces the middle lobes; the end lobe is dilated and its notch linear; the basal lobes are emarginate and suddenly contracted beneath the tubercles, which are smaller than in the last species, and have their upper margins nearly horizontal, by which it may be distinguished from it. The transverse view also has four lobes on each side instead of three. The empty frond is punctate.
Euastrum affine differs from E. pinnatum by its smaller size, by being sinuated, not pinnatifid, and by the lobes being less prominent in the transverse view. In E. pinnatum we find the segments distinctly five-lobed, but in this and some other species the middle lobes are replaced by tubercles more or less developed.
Length of frond 1/230 of an inch; breadth at basal lobe 1/458; breadth at middle lobes 1/659; breadth of neck 1/1204; breadth at end 1/917;
Tab. XIII. fig. 3. a. mature frond with endochrome; b. empty frond;
c. side view; d. end view; e. transverse view.
7. E. ampullaceum --- ; segments short, with inflated base, small intermediate tubercles, and a dilated, notched, terminal lobe.
Euastrum -, Hass. Brit. Freshwater Algae, t. 100. f. 11.
Dolgelley, J. R. Ambleside, Westmoreland, Mr. Sidebotham. Near Tunbridge Wells and near Storrington, Sussex ; and Hampshire, Mr. Jenner.
Frond smooth, twice as long as broad, rather smaller than Euastrum affine. The base is much-inflated, and is separated from the small intermediate tubercles by a slight constriction. The terminal lobe is dilated, its outline usually more convex than that of the other species, and it tapers more gradually into the very short neck, hence it appears more cuneate or fan-shaped; its notch is linear.
Euastrum ampullaceum may be best recognized by its short segments, in which and its broad inflated base it differs from E. affine, whilst the distinctly dilated terminal lobe separates it from E. Didelta.
The empty frond is punctate, and the inflated protuberances on its front surface are indistinct.
Length of frond 1/274 of an inch; breadth of base 1/394; breadth at end 1/788;
breadth of neck 1/1173.
Tab. XIII. fig. 4. a. frond with endochrome ; b. empty frond; c. side view; d. transverse view.
8. E. insigne (Hass.); segments inflated at the base and tapering upwards into a slender neck; end dilated, emarginate; transverse view with two distant lobes on each side and one at each end.
Euastrum insigne, Hass. Brit. Alg. t. 91. f. 2. (1845).
Dolgelley, J. R. Midhurst, and Fittleworth Common near Petworth; and New Forest, Hants, Mr. Jenner. Ambleside, Mr. Sidebotham. Moss Hagg, Banffshire (altitude 3000 feet), Mr. P. Grant.
Frond rather smaller than that of Euastrum Didelta, about three times
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as long as broad; each segment is inflated at its base, the sides of which are entire, and tapers upwards into a slender neck without lateral tubercles; terminal lobe dilated, its notch linear and frequently obscured by the inflated prominences. The end view is cruciform.
The transverse view differs from that of every other species, for in them the outline is elliptical, or broadest at the centre, but in this plant the sides are straight, with a little constriction at the centre and a slight swelling or lobe near each extremity; indeed without the end lobes the form would be nearly quadrangular. The empty frond is punctate.
Mr. Sidebotham has gathered a conjugated specimen of this species near Ambleside.
The inflated base and slender neck, conjoined with its dilated end, are sufficiently characteristic.
To avoid a needless multiplication of synonyms, I have here adopted the name under which Mr. Hassall has figured it in his work on the British Freshwater Algae, although in a paper read before the Botanical Society of Edinburgh I had previously called it Euastrum gracile, and had distributed specimens under that name, from some of which indeed Mr. Hassall obtained his knowledge of the species, a circumstance that he has omitted to notice.
Length of frond 1/232 of an inch; breadth at base 1/416; breadth at end 1/806; breadth of neck 1/1422.
Tab. XIII. fig. 6. a. frond with endochrome; b. empty frond; c. side view; d. transverse view; e. end view.
Heterocarpella Didelta, Turp. Mem. p. 295 (1828).
Common. Carnarvon, Dolgelley, Penzance, &c., J. R. Near Tunbridge Wells; near Battle, Henfield, Midhurst, Sussex; and Hampshire, Mr. Jenner. Westmoreland, Mr. Sidebotham. Aberdeen, Dr. Dickie and Mr. P. Grant.
Falaise, Brébisson. New York, Bailey.
Frond comparatively large, about thrice as long as broad; segments pyramidal, inflated at the base, and tapering upwards into the intermediate tubercles; the neck is broad, and the end slightly dilated, with a terminal linear notch. The end view is bilobed, and the transverse one elliptic with four slight lobes on each side and one at each end. The empty frond is punctate.
Euastrum Didelta differs from the preceding species in the slight dilatation of the end lobes, and in the end view the two lobes are entire.
The sporangia, which I have twice found at Dolgelley, are orbicular, and have subulate spines.
Length of frond 1/185 of an inch ; breadth at base 1/357; breadth at end 1/752; breadth at constriction 1/1250; thickness in side view 1/454.
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Tab. XIV. fig. 1. a. frond with endochrome; b. empty frond; c. transverse view; d. end view.
10. E. ansatum (Ehr.); segments inflated at the base, end tapering upwards to the notched but not dilated extremity; transverse view cruciform.
Cosmarium Didelta, Menegh. Synop. Desmid. in Linnaea l840, p. 219.
Euastrum Didelta, Ralfs, Ann. of Nat. Hist. v. 14. p. 190 (in part) t. 7. f. 2. a, b. (1844); Trans. of Bot. Soc. of Edinburgh, v. 2. p. 127. t. 11.
Euastrum ansatum, Ehr. Infus. p. 162. t. 12. f. 6. (1838).
Euastrum --- , Bailey, in Amer. Journ. of Science and Arts, v. 41. p. 295. t. 1. f. 27. (1841).
Euastrum Didelta, Ralfs, Annals of Nat. Hist. v. 14. p. 190 (in part). t. 7. f. 2. c, d, e, f. (1844); Trans. of Bot. Soc. of Edinburgh, v. 2. p. 127. t. 11.
Euastrum binale, Kütz. Phy. Germ. p. 135 (1845).
Common. North and South Wales, and Penzance, J. R. Hants, Surrey and Sussex, Mr. Jenner. Kerry, Mr. Andrews. Aberdeenshire and Banffshire (altitudes 200-3600 feet), Dr. Dickie and Mr. Grant. Cheshire and Westmoreland, Mr. Sidebotham. Near Manchester, Mr. Williamson. Near Bristol, Mr. Thwaites. Rochdale, Mr. Coates.
France, Brébisson. Germany, Ehrenberg and Kützing. United States, Bailey.
Frond smaller than that of E. Didelta, twice as long as broad; the segments inflated at the base and tapering upwards into a neck, which is not dilated at the end; the terminal notch is linear. The end view has two circular and entire lobes, and the transverse view a single inflation on each side. The empty frond is punctate.
I formerly considered this plant as the young state of E. Didelta, and I am not yet fully persuaded that it is distinct; but as it differs from E. Didelta in every view, and Mr. Jenner, whose opinion I highly value, urges their separation, I have raised this form to the rank of a species: whether it is right to consider it one, experience must decide.
Euastrum ansatum is separated from E. circulare by the absence of the five tubercles at the base of the segments in the front view; in respect of the other species its form is a sufficient distinction.
Length of frond 1/315 of an inch; breadth at base 1/654; breadth at end 1/1298.
Tab. XIV. fig. 2. a. frond with endochrome; b, c. empty fronds; d. side view; e. transverse view; f. end view.
11. E. circulare (Hass.); segments three-lobed, mostly with five basal tubercles; four of them usually disposed semicircularly about the fifth; end notched, scarcely dilated.
beta. Segments emarginate at the sides, the basal portion with five tubercles.
Euastrum sinuosum, Lenormand, in herb. ( 1845).
gamma. Segments emarginate at the sides; tubercles smaller, more numerous and scattered.
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alpha. High Beech, Essex, Hassall. Near Aberdeen, Mr. P Grant.
beta. Dolgelley J. R. Ambleside, Westmoreland, Mr. Sidebotham. Weston Bogs near Southampton, Mr. Jenner.
gamma. Ambleside, Westmoreland, Mr. Sidebotham.
beta. Falaise, Brébisson
As I have seen no authentic specimens, and am not sure whether the number and position of the inflated protuberances are constant, I may have united under this name more than one species. The variety gamma. especially differs from the other forms in the number and arrangement of the tubercles, but as I have seen no specimen of it, and Mr. Jenner only one or two fronds mixed with other Desmidieae, which Mr. Sidebotham forwarded from Westmoreland, I have no means of deciding where it should be placed. At the same time I am unwilling to omit so interesting a form, and as it agrees in outline with the variety beta, I have placed it here, in the hope it may be recognized.
I have gathered near Penzance a single frond, which I suppose maybe the state figured by Mr. Hassall. The protuberances were distinct on one segment, but not on the other. In form it resembled E. ansatum; the inflations on the front surface were its most obvious distinction from that plant; in a transverse view I presume it would resemble the other varieties.
The variety beta. is not uncommon near Dolgelley; the segments are emarginate at their sides and the end lobe is slightly dilated. On the front surface are five protuberances, but their arrangement is different from that in Mr. Hassall's figure; they are also less distinct and sometimes scarcely perceptible. An Euastrum, however, gathered at Falaise, for the sight of which I am indebted to Dr. Dickie, unites the beta. form with protuberances exactly like those represented by Mr. Hassall.
This variety agrees in some respects with Euastrum pectinatum and E. gemmatum, but has a terminal linear notch, and the end view exhibits two nearly quadrate and slightly notched lobes.
Length of frond of var. beta. 1/325 of an inch; breadth at base 1/549; breadth of neck 1/1269. breadth at end 1/1059.
Length of frond of Falaise specimen 1/320 of an inch; breadth at base 1/519; breadth of neck 1/1234; breadth at end 1/1149.
Tab. XIII. fig. 5. a. frond of beta
. with endochrome; b. empty frond; d. transverse view; c. empty frond of gamma.
Tab. XIV. fig. 3. a. frond as figured by Hassall in Brit. Alg. ; b. frond of the Falaise variety; c. end view.
12. E. pectinatum (Bréb.); segments three-lobed; terminal lobe dilated, scarcely emarginate; lateral lobes horizontal, emarginate; end view two-lobed at each end and two lobules on each side.
Cosmarium pectinatum, Bréb. in Menegh. Synop. Desmid. in Linnaea 1840 p. 222.
Euastrum gemmatum, Ralfs, Annals of Nat. Hist. vol. 14. p. 191. t. 7. f. 4.
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Boggy pools; not rare. Dolgelley, Penzance, J. R. Sussex, and Weston Bog near Southampton, Mr. Jenner. Brookhouse Moss, near Congleton, Cheshire; and Ambleside, Westmoreland, Mr. Sidebotham. Glen Derry, Aberdeenshire, Dr. Dickie. Aberdeen and east of the Hill of Fare, Aberdeenshire; and Moss Hagg, Banffshire, Mr. P. Grant.
Falaise, France, M. De Brébisson.
Frond two or three times longer than broad; each segment has a broad basal portion, which is somewhat quadrilateral, horizontal, and at each side emarginate; the neck is short and broad; the terminal lobe is dilated; the sides entire in alpha . and slightly notched in beta; the terminal notch is obsolete.
A transverse view is twice as long as broad, with three lobes on each side and two at each end.
The end view shows that the terminal portion has two lobes at each end and two lobules on each side, one belonging to each lobe. The empty frond is punctate.
Euastrum pectinatum is a very distinct species, and differs from all the preceding in the absence of a terminal notch, in the lobules of the end lobe, and in having the ends emarginate in the transverse view.
I formerly considered this species as the Cosmarium gemmatum of Meneghini's Synopsis. I am indebted to M. De Brébisson for the information that it is distinct, and also for drawings of both plants.
Sporangia gathered at Dolgelley are orbicular, with conical tubercles or short obtuse spines.
Length of frond 1/362 of an inch; breadth at base 1/558; breadth at end 1/776; breadth of neck 1/1126; breadth at constriction 1/2604; diameter of sporangium from 1/490 to 1/440.
Tab. XIV. fig. 5. a. frond with endochrome; b. empty frond; c. frond of var. beta ; d. endview; e. transverse view; f . sporangium
13. E. gemmatum (Bréb.); segments three-lobed; terminal lobe dilated, broadly emarginate; basal lobes horizontal, emarginate, protuberances minutely granulate.
Bogs. Dolgelley and Penzance, J. R. Ambleside, Mr. Sidebotham. Aberdeen, Dr. Dickie and Mr. P. Grant. Weston Bogs near Southampton, and near Pulborough, Sussex, Mr. Jenner.
Falaise, De Brébisson. Nordhausen, Prussia, Kützing.
Frond about twice as long as broad; segments three-lobed, the basal ones horizontal, emarginate, and their projecting parts granulated. The end lobe
Euastrum gemmatum, Kütz. Phy. Germ. p. 134 (1845). Bréb. in lit. cum icone.
Euastrum papulosum, Kütz. Phy. Germ. p. 135 (1845).
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is dilated; the neck is short, and about one-third as broad as the base; the granulated dilatations of the terminal lobe are inclined upwards, hence the end is broadly emarginate. The transverse view is oblong, with three lobes on each side and one at each end. The end view shows that the terminal lobe is cruciform.
Euastrum gemmatum is a small but elegant species, the base being quadrilateral, horizontal, and nearly three times as broad as long. It may be known from all in this section, except E. pectinatum, by the absence of a linear terminal notch, and from that species it may be distinguished by the smallness of the end lobe and the outward direction of its angles, and by the minute granulation of the projecting parts.
M. De Brébisson has kindly furnished me with drawings of Euastrum gemmatum, Bréb., and E. papulosum, Kütz., the latter of which be reduces to a variety of the former in a MS. list of the species of this genus; but I must confess that I know not how to make even this distinction between them.
Length of frond 1/442 of an inch; breadth at base 1/641; breadth at end 1/1219; breadth of neck 1/1497.
Tab. XIV. fig. 4. a. frond with endochrome; b. empty frond; c. side view; d. end view; e. transverse view.
*** Frond without a distinct terminal lobe, and frequently having a process or an acute angle at the corners of the terminal portion.
14. E. rostratum (Ralfs); frond oblong; ends protuberant, emarginate and angular, with a horizontal spine on each side.
Dolgelley and Penzance, J. R. Sussex, Mr. Jenner. Near Aberdeen, Dr. Dickie and Mr. P. Grant. Moss Hagg between Tomantaul and Lochavon (alt. 3000 feet), Banffshire, Mr. P. Grant. Near Ambleside, Mr. Sidebotham. New York, Bailey.
Frond very minute, about twice as long as broad; segments obscurely three-lobed, or rather having a broad basal portion, which is emarginate at each side and connects itself by a broad short neck with the terminal lobe. This terminal portion has on each side a horizontal, subacute, beak-like process, and is prominent, emarginate and angular.
Euastrum rostratum, like the species in the preceding section, is contracted (though less decidedly) into a neck, and also has emarginate sides; but it differs from them in its much smaller size, and especially in the horizontal processes of its end lobe. The angular and less prominent ends distinguish it from E. elegans.
A single sporangium which I gathered at Dolgelley was spinous, like that of E. elegans, but larger.
Length of frond from 1/649 to 1/508 of' an inch; breadth from l/1000 to 1/714.
Tab. XIV. fig. 6. a, b. fronds with endochrome.
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15. E. elegans (Bréb.); frond oblong; ends emarginate, pouting and rounded.
alpha. segments slightly constricted beneath the end lobe, which has on each side a short horizontal spine.
beta. inerme; segments sinuated rather than lobed, and without spines.
gamma. spinosum; segments sinuated rather than lobed, and having two or more spines directed obliquely outwards.
Cosmarium elegans, Bréb. Menegh. Synop. Desmid. in Linnaea 1840, p. 222.
Common. Dolgelley, Carnarvon, Penzance, &c., J. R. Cheshunt, Mr.Hassall. Barmouth, Rev. T. Salwey. Near Southampton; Reigate; frequent in Sussex, Mr. Jenner. Ireland, Mr. Andrews. Hanham near Bristol, Mr. Thwaites. Yate near Bristol, Mr. Broome. Cheshire and Westmoreland, Mr. Sidebotham. Aberdeenshire and Banffshire (alt. 50 -3000 feet), Mr. P. Grant.
Falaise, Brébisson. Germany, Kützing. New York, Bailey.
Frond very minute, and about twice as long as broad; the segments emarginate at their sides, and the ends protuberant, rounded and emarginate.
The sporangia are orbicular and spinous; they have been gathered at Yate by Mr. Broome, and by myself near Dolgelley.
Euastrum elegans is a pretty but variable little species; one state of it closely approaches E. rostratum, with which it agrees in being somewhat contracted beneath the terminal lobe, and also in its horizontal, though smaller, spines; but all its forms differ from that species by having the prominent ends not angular but rounded.
The variety beta
. has no spines and no distinct neck; the sides are undulated rather than lobed, and the ends broadly rounded.
The variety gamma
. is distinguished by the spines being directed obliquely forwards, and besides those on the terminal portion it has usually one or two at the sides; there is no distinct neck, and the end is more protuberant and narrow than in the other forms. The spines of its sporangia are more numerous and slender than those in the typal form. I have not seen sporangia from a sufficient number of stations to decide whether differences in their spines indicate different species; but I believe that the number and shape of the spines vary even in the same species.
Length of frond of alpha
. 1/888 to 1/445 of an inch; breadth 1/1441 to 1/714; diameter of sporangium 1/905; length of spine of sporangium 1/3086. Length of frond of beta
. 1/421; breadth 1/654. Length of frond of gamma
. 1/884; breadth 1/1388; diameter of sporangium 1/980; length of spine 1/2631.
Tab. XIV. fig. 7. a, b, c. fronds of alpha. with endochrome ; d. sporangium; e. frond of var. beta; f. mature frond of var. gamma; g. side view; h. transverse view; i, k. dividing fronds; l. sporangium.
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Euastrum spinosum, Ralfs, Annals of Nat. Hist. v. 14. p. 193. t. 7. f. 6. (1844); Trans. of Bot. Soc. of Edinburgh, v. 2. p. 129. t. 11. Hass. Brit. Algae, p. 384.
Euastrum elegans, Kützing, Phycologia Germanica, p. 135 (1845).
16. E. binale (Turp.); segments concave or truncate at the end; not projecting beyond the acute angles.
Penzance and Dolgelley, J. R. Henfield and elsewhere in Sussex; Hampshire, and Reigate, Surrey, Mr. Jenner. Hill of Rhoil (alt. 1600 feet), Aberdeenshire, Dr. Dickie. Near Aberdeen, Mr. P. Grant. Ambleside, Mr. Sidebotham. Near Bristol, Mr. Thwaites.
Falaise, Brébisson. New York, Professor Bailey.
Frond very minute, about twice as long as broad; segments inflated at the base, either entire or bicrenate at the sides, slightly contracted upwards and rather dilated at the end. The terminal notch is broad, and forms a concavity between the angles.
The variety beta
. (which may prove a distinct species) differs in its quadrilateral form and in its truncate ends, which have a small but distinct notch at the centre. The acute angles are slightly prolonged horizontally; the sides of the segments are somewhat crenate, and the frond is rough, with a few scattered and very minute granules.
Euastrum binale is distinguished from the two preceding species by its con-cave or truncate ends and its notch, the sides of which do not project beyond the lateral spines or angles.
A solitary conjugated specimen was gathered near Bristol by Mr. Broome, but the sporangium was not completely developed.
Length of frond (Tab. XIV. f. 8. c.) 1/1428 of an inch; breadth 1/1945: length of frond (f. 8. d.) 1/1179; breadth 1/1396: length of frond (f. 8. e.) 1/1968; breadth 1/2403: length (f. 8. f.) 1/1106; breadth 1/1326.
Tab. XIV. fig. 8. a, c, d, e. fronds with endochrome; b. empty frond; g. transverse view; h. a specimen conjugating; f. frond of var. beta.
Cosmarium binale, Menegh. Synop. Desmid. in Linnaea 1840, p. 221.
Euastrum binale, Ralfs, Annals of Nat. Hist. v. 14. p. 193. t. 7. f. 7. (1844); Trans. of Bot. Soc. of Edinburgh, v. 2 . p. 130. t. 11. Hass. Brit. Alg. p. 384.
17. E. cuneatum (Jenner); segments cuneate, not lobed; terminal notch not linear.
Aberdeenshire, Dr. Dickie. Dolgelley, J. R. Parham Old Park near Storrington, Sussex, Mr. Jenner.
The frond is larger than that of any other species in this section, and about three times longer than broad; the segments are nearly quadrilateral, broadest at the base, and sloping upwards; the ends are truncate, with a short linear notch at the centre. The sides are not sinuated, and I have not detected any inflated protuberances.
The frond has so great a resemblance to some states of E. crassum, that, although its segments are not lobed, I think it may prove to be a variety of
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that species; for in Dr. Dickie's specimen I observed a frond, one segment of which answered the above description, whilst the other had a distinct, cuneate, terminal lobe, as in E. crassum. But as I lost the frond before I was able to obtain a satisfactory view of it, and as the form here described is so peculiar, and has been noticed in widely separated stations, I have given it the rank of a species, awaiting the result of further observations.
Length of frond 1/208 of an inch; breadth at base 1/420; breadth of end 1/740.
Tab. XXXII. fig. 3. a. frond with endochrome; b. transverse view.
18. E.? sublobatum (Bréb.); segments subquadrate, somewhat contracted beneath the end; the end margin slightly concave.
Euastrum? sublobatum, Brébisson, in lit. cum icone (1846).
Machynlleth and Dolgelley, North Wales, J. R. Ambleside, Mr. Sidebotham.
Falaise, Brébisson.
Frond twice as long as broad, and rather larger than that of E. elegans; the segments nearly quadrate, their sides and end somewhat sinuated, and their base slightly inflated.
Euastrum sublobatum has nearly as good a claim to a place in Cosmarium as in this genus. The terminal notch is here replaced by a slight concavity, and in their form its segments are not unlike those of Cosmarium quadratum; but their constricted appearance, from the more strongly-marked lateral concavities, inclines me to retain this species in Euastrum.
Length of frond 1/523 of an inch; breadth at base 1/646; breadth at constriction 1/3246; breadth of end 1/1028.
Tab. XXXII. fig. 4. a. frond with endochrome; b. empty frond; c. transverse view; d. end view.
