70 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 antherozoid similar 

 in form to the swarm-spore. Attempts should also be 

 made to observe the germination of the oospore. 



With (Edogomum it will be well to compare species of Bulbo- 

 cTicete, which resembles (Edogonium 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 cat le troughs, and fountains: 

 it occurs attached to stones and other objects near 

 to the surface, and is to be recognised as a delicate, 

 filamentous, 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 



