PRACTICAL BOTANY 



iii. The hyaline receptive spot. 



iv. In old oogonia the mature oospore with thick 

 wall, and dense contents. 



The antheridia, which are smaller and shorter 

 cells than those of the normal filament : each divides 

 into two cells, the contents of which, without further 

 division, escape as a motile yellow spermatozoid 

 similar in form to the swarm-spore. Attempts should 

 also be made to observe the germination of the 

 oospore. 



With CEdogonium it will be well to compare species of Bulbo- 

 chcete, which resembles CEdogonium in its fresh- water habit, its 

 mode of attachment, and in its processes of cell-division and re- 

 production ; but differs from it in its profuse branching, and in 

 the presence of peculiar long bristles with swollen bases, which 

 are borne on the ends of the branches. 



ULOTHRIX ZONATA, Ktz 



This Alga is to be found, especially in spring and 

 early summer, in slow-flowing streams, and ponds of 

 fresh water, or in cattle troughs, and fountains : it 

 occurs attached to stones and other objects near to the 

 surface, and is to be recognized as a delicate, filament- 

 ous, unbranched organism of a bright green colour : 

 it is attached by an attenuated base to the substratum, 

 and the simple filaments are composed of numerous 

 cells, each having a median zone-like chromatophore ; 

 hence the specific name. 



Mount some filaments of the Alga in fresh water, 

 and cover with a glass slip : neglecting for the present 

 those specimens in which the reproductive processes 



