CONFERVOIDE^ HETEROGAMY. 121 



immediately above the first one, followed by a similar 

 splitting of the outer layer of the wall all round the cell 

 and immediately over the thickened portion, which in turn 

 elongates and forms a new cell, pushing the two upper 

 ones before it, so that the original apical cell continues to 

 remain so throughout the entire life of the plant. We have 

 now two frills, or free margins of cell-wall, at the base of 

 the second cell, and as this process is often repeated from 

 six to ten or more times by the same cell, the result is 

 a corresponding number of free margins of the split 

 cell-wall, that have received the name of caps. Any one 

 of the daughter-cells resulting from this method of division 

 may in turn become a generating cell, the number of caps 

 or free margins indicating the number of cells produced 

 by a given generating cell. 



The asexual mode of reproduction is by motile zoospores 

 formed by rejuvenescence in certain of the cells of a fila- 

 ment. The zoospores are very large, and the anterior 

 colourless end is furnished with a tuft of cilia ; a well-defined 

 nucleus and an orange-red spot are also present. 



The sexual mode of reproduction is effected by anther- 

 ozoids and oospheres. The antherozoids originate in 

 two different ways. In one method the antheridia are 

 cells forming the filament, but recognized by being much 

 shorter than the vegetative cells,, and may be scattered and 

 solitary, or following each other in considerable numbers. 

 In most instances the cells destined to become antheridia 

 divide into two mother-cells by the formation of a horizontal 

 or transverse septum, the contents of each mother-cell be- 

 coming transformed into an antherozoid. The antherozoids 

 are furnished with a tuft of cilia like the zoospores, but are 

 much smaller. 



