188 



STRUCTURAL BOTANY 



FIG. 80. Ectocarpus siliculosus. A, part 

 of a branch, bearing two plurilocular 

 sporangia (sp), from one of which the 

 zoo spores (z) are escaping. Magnified 330. 

 B, female cell ($) which has come to rest, 

 with numerous male cells swarming 

 around it. C, two stages of conjugation. 

 B and C magnified 790. (A after Thuret ; 

 B and C after Berthold.) 



protoplasmic bodies 

 are thus brought to- 

 gether, until finally 

 the active and the 

 resting cell com- 

 pletely fuse into one. 

 We see that this 

 process, by which 

 a zygospore is pro- 

 duced, is a step in 

 advance of the con- 

 jugation of Ulothrix, 

 for in the Ectocarpus 

 there is so far a dif- 

 ference between the 

 two cells, that at the 

 moment of fusion one 

 is at rest and the 

 other active, though 

 previously they had 

 both behaved quite in 

 the same way. We 

 may look upon this 

 as the first slight 

 approach towards the 

 differentiation of sta- 

 tionary ovum and 

 motile spermatozoid. 

 In spite, however, of 

 this distinction, both 

 cells alike are capable 

 of independent ger- 

 mination as asexual 



