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The Characterisation of Cryptogames and the Phylogenetical Relations between Cryptogames and Phanerogames

The first (incomplete) works dealing with the characterisation of cryptogames were published at the beginning of the 18th century. J. J. DILLENIUS (1687 - 1747; professor at Oxford) wrote his "Historia muscorum" in 1741. He still took the powder contained in the capsules of moss for pollen. TOURNEFORT corrected him. In 1675, F. V. STERBEECK (1631 - 1693) published a book on fungi "Theatrum fungorum" published in Antwerp. H. F. LINK began a system of fungi and sponges that was completed by C. G. NEES von ESENBECK, who published it in 1817 (Würzburg). A. W. ROTH (1737 - 1834) was preoccupied with algae and, in 1797, published fundamental rules for the differentiation of freshwater algae discovered with the aid of microscopes. BONAVENTURA CORTI observed in 1774 the circulation of the sap contained in the sections of Chara. And the clergyman J. P. VAUCHER from Geneva described the connection of two pipes of Spirogyra plus the resulting generation of little "germination spheres", as well as their accumulation at narrowed spots. In 1803, he came to the conclusion that this conjugation has to be understood as a sexual act, a view that was confirmed by deBARY in 1858. K. C. SCHMIEDEL (1718 - 1793) began with the examination of the reproductive organs of marchantiatae and other cryptogames, but the basis for all further examination became the works of J. HEDWIG (1730 - 1799) from Siebenbürgen. He was a professor of medicine and later of botany at Leipzig. In 1774, he discovered the reproductive organs of bryophytes and from 1782 - 1784 he established proof that moss has to be included into the system of LINNÉ. The inspector of the botanical garden of Berlin, Fr. OTTO (1784 - 1856) was the first who was able to grow ferns out of spurs. He founded one of the biggest fern collections of Europe in Berlin.

A very detailed picture of lower fungi and their developement was given by the botanist ANTON de BARY (1831 - 1888) after twenty years of research. He worked first in Freiburg, later in Strassburg. de BARY was not satisfied with study-trips to the habitats of the different states of development of the fungi alone but did also cultivate single species in order to study their whole developement. He, too, succeeded in the observation of the penetration of parasitic fungi into healthy plants and animals and could show that fungi can exist in living plant material. In 1863, he proved that the whole ascus of the ascomycetes is itself the product of the sexual act that takes place at the hyphen of the mycel.

During the 1840s, the research done in of a lot of fields that had formerly drifted apart gathered again. The microscopical procedures had advanced further (see above) and it showed that they were indispensable for the study of cryptogames, too.

The decisive breakthrough concerning the phylogenetic relation between cryptogames and phanerogames (flowering plants) was made by W. HOFMEISTER (1824-1877; professor of botany at Heidelberg since 1863, in Tübingen since 1872). He placed the gymnosperms, that had been related to the dicotyledons before, as a third class next to the mono- and dicotelydons and recognized the homology between the reproductive mode of higher cryptogames and the seed production of phanerogames. Among his most important research was the study on the developement of the embryo of phanerogames, performed in 1851. He was of the opinion that the embryo sac containes a "Keimkörperchen", a small body of germination, even before pollination that is stimulated by the arrival of the pollen tube to develop an embryo. He trailed step by step, cell by cell, the formation and organisation of the seed bud, pursued the nature of the embryo sac and the pollen, as well as the developement of the embryo from the pollinated egg. Furthermore, he understood the significance of the alternation of generations for the elucidation of the relations between as differently organised groups as the marchantiatae, bryatae, ferns, horsetails, gymnosperms, and mono- and dicotyledons.With his work, he founded the base for drawing up a true natural system of plants.

The alternation of generations is most pronounced in ferns and mosses, though the selaginellales the display the same pattern. They produce small male microspores and large female megaspores. With the occurrence of this interim solution the seed formation of conifers becomes understandable: their embryo sac corresponds to the megaspore [the prothallium (gametangium) degenerates to the endosperm], while the pollen are homologous to the microspore.

As from now the evolutionary connections formed the leitmotif of botanical research. Around this central theme the research into the evolution of all sorts of plant groups became possible. Only eight years after HOFMEISTER's investigations DARWIN's theory of evolution was published. The relations between the great taxonomical groups of the plant kingdom had already been so safely confirmed that no inconsistency between observation and theory arose. The evolution of plants thus became an important support for the theory of evolution.

© Peter v. Sengbusch - b-online@botanik.uni-hamburg.de