ALGM. 



231 



forms, as in Vaucheria, the oosphere, in the interior of which the grains of chlorophyll 

 are densely crowded. The part of the oosphere which faces the opening of the 

 oogonium consists simply of hyaline protoplasm. The opening of the oogonimn is 

 produced in a variety of ways. In some species of Qildogonium and all of Bulbochaete its 

 wall has an oval hole in its side, out of which the colourless part of the oosphere 

 protrudes in the form of papillae, and takes up the spermatozoids. In some species 

 of CEdogonium (Fig. 163, A, B), on the other hand,- the oogonium-cell splits, as 

 when the swarm-spores are escaping ; and the otherwise straight row of cells of the 

 filament thus appears as if broken at this 

 spot. In the lateral crevice appears some 

 colourless mucilage, which the observer 

 can actually see take the form of an open 

 beak-like canal (Fig. 163, 5, a), through 

 which the spermatozoid enters. It mixes 

 with the hyaline part of the protoplasm of 

 the oosphere while it melts away. Imme- 

 diately after fertilisation the oosphere sur- 

 rounds itself with a membrane, which after- 

 wards, like its contents, assumes a brown 

 colour ; but in Bulbocha!te the contents of 

 the oospore thus formed is of a beautiful 

 red colour. The oospore remains enclosed 

 in the membrane of the oogonium, which 

 separates from the neighbouring cells of the 

 filament and falls to the ground, where the 

 oospore passes its period of rest. When it 

 awakes to new activity, the oospore does 

 not itself grow into a new plant ; but in 

 Bulbochxte, where this process has been 

 observed, its contents divide into four 

 swarm-spores, which escape together with 

 the inner skin of the oospore, and after 

 this latter is dissolved, swim about. After 

 becoming stationary each grows into a new 

 plant'. 



The Coleoclisetee 2 are small (about 

 1-2 mm.) fresh-water Algae, chlorophyll- 

 green and constructed of branched rows 

 of cells, attached in standing or slowly run- 

 ning water to the submerged parts of other 

 plants {e.g. Equisetum), and forming circu- 

 lar closely-attached or cushion-like discs 

 Their chlorophyll assumes the form of 



parietal plates or of larger lumps ; and the name of the genus Coleochsete (sheath- 

 hair) is due to the circumstance that certain cells of the thallus form lateral 

 colourless bristles fixed in narrow sheaths (Fig. 164, J, F). If the phenomena of 

 growth of the different species are compared, two extreme cases are seen, united by 



Fig. 164.—^ an asexual plant of Coleochate soluta (x^^o) 

 B a piece of a similar disc ; the letters a-g indicate the sue 

 cessive dichotomous branchings of the terminal cells (after 

 Pringsheim). 



^ [Confervacese are a group of green filamentous Algae. They are reproduced by zoospores 

 (Cladophora, Chroolepus). Colin has described the sexual reproduction of Sph<xroplea attmdina in 

 Ann. des Sci. Nat. 4th ser. vol. V. 1856. — TJlvaceae agree with ConfervaccDc, but are expanded 

 into a membrane (forming a tube in Enteromorpha) and are not filamentous. They are only known 

 to be propagated by zoospores. — Ed,] 



' Pringshcim in Jahrbuch fiir wissenschaftliche Lotanik, vol. II. p. I. 



