CEDOGONIACE.E. 149 



breaking away of the wall of the mother cell. In this manner the new 

 cell soon attains a length equal to the one from whence it sprung (the 

 successive stages shown on Plate LVII, figs. 1 to 4). When the young 

 cell has matured it becomes in turn a mother cell, the splitting round is 

 repeated, a second streak or cap is carried upwards, and thus as many as 

 four, five, or six successive cells are formed, as indicated by the four, 

 five, or six striae or caps which may be counted at the apex of a cell. The 

 number of caps corresponding to the number of cells produced in this 

 manner consecutively immediately beneath the caps. 



Asexual reproduction takes place by the formation of a single zoospore 

 in one of the cells of the filament (Plate LVII, fig. 15). It is of a globose 

 or somewhat ovate form, furnished near its apex with vibratile cilia (fig. 

 14). When mature it escapes by rupture or fissure of the mother cell, 

 moves about for awhile, then becomes attached by the ciliated end, and 

 ultimately developes into a young plant. 



Sexual reproduction is varied in three ways. In the monoecious species 

 the oogoniuin is an inflated cell, more or less globose, enclosing a single 

 oospore of similar form. The oogonium is either perforated by a pore, 

 or splits round and opens with a lid or operculum. The same thread 

 bears above or below the oogonium very much shortened cells, in which 

 one or two active spermatozoids are produced. These escape when 

 mature, and fecundate the oospore through the perforation or opening of 

 the oogonium, after which they disappear, and the oospore ripens into a 

 perfect, fertile, resting spore. 



In the dioecious species there are two modes of sexual reproduction. 

 In one group of species the males are dwarf, almost might be called 

 antheridia. The oogonia and oospores are the same as in the monoecious 

 species. In like manner there are also abbreviated cells in some other 

 part of the same thread, but these do not produce spermatozoids, but 

 androspores, small active ciliated bodies, which move about for a time, 

 and then attach themselves either upon or near the oogonia, grow into 

 the form of an inverted flask (figs. 8 to 10), being supported by a more or 

 less elongated stein, and constitute the dwarf male (nannandrous) plants, 

 the cells at the apex of which contain the spermatozoids, the upper cell 

 opening by a lid, or cap, to permit of the escape of its contents, which 

 fertilize the oospore as in the previous method. 



The second group of dioecious species have male filaments, which in 

 all respects resemble the sterile females, except that they are usually a 

 little thinner. The female filaments produce only the oogonia. 

 The male filaments, in certain abbreviated cells, give origin 

 to the spermatozoids, which in due time escape and fertilize the 

 oospores of the female plants. Thus, in the first group, the dwarf males 

 are generated in certain privileged cells of the female plants, whilst in 

 the second group the male and female filaments are from the first dis- 

 tinct. The former are called nannandrous species, the latter macran- 

 drous. 



The fertilized oospore becomes a resting spore, which ultimately 

 passes through the following stages : Previous to germination the spore 

 has an egg-shaped figure ; the cell contents are densely crowded, and 

 composed of minute brownish-green granules, closely surrounded by a 

 distinct cell-membrane. Outside this membrane there is found besides 

 quite a distinct cell-membrane. Upon germination there are formed in 

 both membranes slit-like openings, whereupon the cell contents emerge, 

 surrounded by an extremely delicate hyaline covering. The cell contents 

 are composed not of one, but usually of four green masses, each sur- 

 rounded by its cell-membrane. Sometimes also as it appears, abnor- 

 m ally, the masses are two or three in number. The four cells which 

 proceed from germination possess an oval form, and their cell-membrane 

 is hyaline. After the contents of the spore have emerged there remains 



