84 AQUATIC PHYCOMYCETES 



matic in optical section, as it is in the resting spore of Blastocladia. 

 whereas the inner wall is thin and solid. Other curious types of orna- 

 mentation are described by Scherffel {op. cit.). The origin of the pe- 

 culiar zones of gelatinous material surrounding the resting spores and 

 sporangia in Rhizophydium coromtm (p. 251) is unknown. Hanson 

 (1945b) suggested that they may be a protoplasmic exudate which is 

 passed through the wall to the outside. 



The precise method by which ornamentation on the resting spore 

 is produced is not well understood. In Rhizophydium asterosporum 

 (Scherffel, 1925b) the incipient and as yet thin-walled resting body 

 forms protrusions which become filled, as the spore matures, with solid 

 refractive often stratified material. In those spec'es of Rozella that 

 have a spiny-walled resting spore (Cornu, 1872a; Foust, 1937) the 

 echinulations are described as originating in a clear zone which en- 

 velops the densely granular main body. In Rozella allomycis (Foust, 

 op. cit.) minute granules appear in the clear enveloping material and 

 align themselves at right angles to the spore wall. They then fuse linearly 

 to form the tenuous spines (Fig. 14 A, p. 179). 



Germination of the resting spores has been observed among repre- 

 sentatives of a number of different genera. The factors which induce 

 it are not known with any preciseness. Generally, as in Rhizidium 

 mycophihun (Nowakowski, 1876a) and Polyphagus euglenae (Nowa- 

 kowski, 1876b; Wager, 1913), a rest period of a month or more appears 

 necessary. Resting spores of Rhizophydium ovation (Couch, 1935a) 

 and Rhizophydium sp. (Karling, 1939c), however, may undergo ger- 

 mination in from two to five days after their formation, only a short 

 period of dormancy being required. In by far the majority of instances 

 in which germination has been witnessed the resting structure func- 

 tioned as a prosporangium {Polyphagus, Entophlyctis, Endochytrium, 

 Diplophlyctis, Megachytrium, Chytridium, Siphonaria, Rhizophydium. 

 and others). In so doing either the wall of the spore cracked or a pore 

 was formed through which the contents emerged, surrounded by a 

 thin membrane. This structure was converted into a zoosporangium 

 attached to the now empty resting body and discharged its zoospores 

 in the same fashion as the zoosporangium formed on the thallus, that 

 is, either operculately or inoperculately (Fig. 23 C, p. 385; Fig. 25 G, 



