THE PLOB \ ' >F M.l'.i; LSK \. 



1. BOTRYDIUM Wallr. in *.nn. Bot. L815, p. 153. 



The characters of the family. According to Rostaflnski and Woronio the 

 genus has several modes of reproduction: ", l<y cell-division; i>. by the 

 formation of macrospores; c, by the formation ol zoospores,] froi 



vegetative plant. 2 from tho root cells. 

 Etymology: (J rook, dimin. from ><-,./■*. a cluster. 



Botryriiiiin <> mini latum (L.) Gbev. AJg. Brit. t. XIX. 1830. 

 Ulva granulata L. Sp. PL 1164, L753. 



The characters of the genus. Common every where on moist earth. PL XII 

 Pig. 1, a, b, c, d, e, f. 



Family. SAPROLEGNIACEAE.* 



Mycelium well developed, filaments branching, without septa; asexual reproduction 

 chiefly by biciliate zoospores arising in zoosporangia: sexual reproduction by oogonea and 

 autherids, generally borne upon short lateral brauches. 



Aquatic fungi, mostly saprophytes, rarely parasites, growing in pure water upon 

 organic substrata. The most common situation is upon dead tish and insects, from 

 which grow out the often very long, much branched filaments bearing at the ends the 

 more or less cylindrical zoosporangia. The protoplasm of the zoosporangium breaks up 

 into a number of globose zoospores which behave variously iri the differenl 

 Diplanetism is, however, typical of most of the genera. In sucli the biciliat 

 swarm out of the zoosporangium and become encysted. Bach zoospore breaks oul of 

 the cyst after a short rest, swims about for a time, is encysted again, and finally grows 

 out into a hyphal filament. In two genera tho first swarming Btage is Lacking, and in 

 another the spores encysted within the sporangium grow directly into germinating flla 

 ments. In addition to zoosporangia, asexual reproduction may take place by means of 

 resting sporangia and chlamydospores. 



The oogones are generally terminal upon short lateral branches, though they may 

 arise at the end of the main filament, or, rarely, they may be intercalated in it. They 



are usually globose, sometimes cylindrical, in form, and contain \-> ae\ era! oospheres 



In monoecious species the antherids are formed upon branches arising Dear the I 



the oogone, or from the main filament in close proximity to tli gone; in dioecious 



species they occur upon separate filaments at the end of the lateral branches At the 

 time of fertilization the antherids send out tubes which pierce the oogone, hut alw iys 

 remain closed at the tip. After this pseudo-fertilization, the oospheres surround them- 

 selves with a thick membrane and become oospores which germinate directly Into a 

 hyphal filament. 



The Saprolegniaceae show on the one hand a very close relationship to the Pan 

 aceae, and on the other a close connection, through Pythium, to the Pcronoqx 

 In their hysterophytic habit they resemble the latter. Genetically, however, they shon 

 a much closer connection with the Vaucheriaceae, of which tiny are probably t.> he oon 

 sidered as forms greatly modified by a change of habit. 



SYNOPSIS 



Zoospores rarely encysted in zoosporangium. escaping through an apical papilla, 



Saprolt [i a in 

 Zoospores always encysted in zoosporangium, escaping through lateral openings, 



, IC/lUt 



By Frederick E. Clements. 



