a8o THALLOPHVTES. 



out of which proceed very small male plants (dwarf males). Several generative cycles 

 or only one may be completed in a vegetative period. The zoogonidium is formed in 

 an ordinary cell of the filament (sometimes even in the first cell, Fig. 182, E) by the 

 contraction of its whole protoplasmic substance ; it becomes free from the mother- 

 cell, the cell-wall splitting by a transverse slit into two very unequal halves (as in the 

 division of the cells) (Fig. 182, yl,B,E). It is at first surrounded by a hyaline mem- 

 brane, which however it also breaks through. At its hyaline end — the anterior end 

 during the swarming — it is encircled by a circlet of numerous cilia. This end lies 

 laterally in the mother-cell, and, after the movement ends, becomes the lower attached 

 end which grows out into a rhizoid ; the direction of growth of the new plant is thus 

 at right angles to that of the mother-cell. The antherozoids are very similar in form to 

 the zoogonidia, but much smaller (Fig. 183, D, «); their motion, due to a circlet of 

 cilia, is also similar. The mother-cells of the antherozoids are cells of the filament, 

 but shorter and not so rich in chlorophyll as the vegetative cells; they lie either 

 singly or in groups (sometimes as many as twelve) above one another. In most species 

 each antheridium-cell divides into two equal special mother-cells, each of which produces 

 an antherozoid ; they escape by the splitting of the mother-cell (as in the case of the 

 zoogonidia) (Fig. 183, D). The androgonidia from which the dwarf male plants arise 

 are produced from mother-cells similar to those which give birth to the antherozoids 

 (without formation of special mother-cells). After swarming they fix themselves to a 

 definite part of the female plant, on or near the oogonium, and after germination produce 

 at once the antheridium-cells, and in them the antherozoids (Fig. 183, ui, B, m, m). The 

 oogonium is always developed from the upper daughter-cell of a vegetative cell of the 

 filament which has just divided, and immediately after the division swells up into a 

 ; spherical or ovoid form. In Bulbochaete the oogonium is always the lowest cell of a 

 fertile branch. This is not opposed to the law of growth above-mentioned, inasmuch as 

 the mother-cell of a branch fulfils at the same time the function of its basal cell ; the 

 oogonium of Bulbochsete is never the first cell of a branch, since this is always developed 

 as a bristle. The oogonium becomes at first more completely filled with contents 

 than the remaining cells ; immediately before fertilisation the protoplasm contracts and 

 forms, as in Faucheria, the oosphere, in the interior of which the chlorophyll granules 

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

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

 produced in a variety of ways. In some species of CEdogonium and all of Bulbochsete 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 antherozoids. In some species of 

 CEdogonium (Fig. 183, A, B), on the other hand, the oogonium-cell splits, as when the 

 zoogonidia are escaping ; and the otherwise straight row of cells of the filament thus 

 appears as if broken at this spot. In the lateral fissure appears some colourless muci- 

 lage, which the observer can actually see take the form of an open beak-like canal (Fig. 

 183, B, z), through which the antherozoid enters. The antherozoid coalesces with the 

 hyaline part of the protoplasm of the oosphere and disappears^. Immediately after 

 fertilisation the oosphere surrounds itself with a membrane, which afterwards, like its 

 contents, assumes a brown colour ; but in Bulbochsete the contents of the oospore thus 

 formed is of a beautiful red. 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 zoospores, 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. 



* In O. diplandrum, discovered by Juranyi, the large antherozoids creep in an amoeboid manner 

 over the oogonium until they reach the canal, which they slowly enter. 



