CHAPTER IIT. 



OF VEGETAL GENERATION. 



ASEXUATE generation is observable in certain algae, especially the 

 confervae. It is accomplished by endogenesis. The protoplasm of 

 certain cells contracts first of all, by separating from the wall, and 

 usually divides afterwards, segmentises into many new cells. 

 Then the enveloping membrane of the mother cell opens and 

 is reabsorbed. The daughter cells escape and swim in the 

 water, eddying, thanks to the movements of two or more 

 vibratile cilia. These zoospores, as they are thus called, end 

 by fixing themselves and germinating (Fig. 44). 



Other algae are endowed with sexuate generation, either in 

 its simplest mode, which is conjugation, or in its complete mode, 

 with male cell, female cell, and fecundation. In the first case 

 (ulothrix, chlamydococcm, pandorina) two cells analogous to the 

 zoospores in movement meet and melt into each other. When 

 there is sexuality, the phenomena still offer great simplicity 

 The female element is represented by a cell, whose protoplasm 

 contracts while separating from the cellular wall. This small 

 protoplasmic mass, thus modified, and ready to evolve, is called 

 oosphere, and the envelopment is called oogon. In other cells 

 the protoplasm transforms itself into mobile elements very 

 analogous to the spermatozoaries of animals. These fecunda- 

 tory elements are denominated anther ozoids, and the cell which 



