314 



Ulotrichales 



almost colourless and usually smaller than the adjacent vegetative cells 

 (figs. 205 A and 206 an). Each antheridial cell gives origin to one, two 

 (or three ?) antherozoids, which are much smaller than the zoogonidia, pear- 

 shaped, quadriciliated, and with a much reduced chloroplast (fig. 205 C). 

 When they first escape they pass into a hyaline vesicle, but the latter 

 undergoes rapid dissolution and sets them free. The antherozoids swim 

 about very rapidly, but the movements of the oospheres are very feeble. 

 The feature of greatest interest in the sexual reproduction of Aphanochazte 

 is the fertilization of the oosphere outside the oogonium. The antherozoid 

 fuses with the receptive spot of the oosphere by its pointed colourless end 

 (fig. 205 D). The oospore surrounds itself with a thick wall and undergoes 

 a period of rest, becoming filled with a red oil. Its germination has not yet 

 been observed. 



00 



oo' 



Fig. 206. Aphanochsete repens A. Br. A, vegetative plant in outline; B and C, plants with na- 

 theridia (an) and oogonia (oo) ; oo', oogonium from which oosphere has escaped. All x 520. 



The genus Aphanochsete is exclusively freshwater and is widely distributed all over the 

 world. There are probably several species, of which A. repens A. Br. is much the most 

 frequent. This Alga is a common epiphyte on larger filamentous Algee, such as CEdogonium, 

 Cladophora, Rhizoclonium, Mougeotia, etc. When attached to the leaves of Elodea, to 

 Lenina, etc., the thallus is often much branched, the branches of the epiphyte frequently 

 following the contours of the epidermal cells and so forming a reticulum (G. S. W., '99 ; 

 '04, fig. 19 B). 



Chodat found that in cultures the setae were sometimes replaced by branches, a fact 

 which clearly indicates that Aphanochsete is nearly related to the Chaetophoracese. 



There does not appear to be any sufficient reason for separating Gonatoblaste Huber ('92) 

 from Aphanochsete. 



Family Coleochaetaceae. 



In this family there is but one genus Coleochtete Brebisson (1844) 

 which as regards its sexual reproduction is on a distinctly higher plane 

 than any of the other genera of Green Algce. The thallus is attached to 

 the stems and leaves of aquatic macrophytes, and is either discoidal or forms 

 cushion-like growths enveloped in mucilage. In the discoidal forms the 



