BLASTOCLADIALES 607 



simple, it may consist either of an anchored reproductive rudiment 

 (Fig. 45 A) or a basal cell and the rudiment of one or more reproductive 

 structures (Figs. 45 E, p. 661 ; 46 D, p. 680). In other forms it is more 

 elaborate with the basal cell bearing distal branches (Fig. 46 A) or 

 pseudoseptate branched hyphae of unlimited powers of growth (Fig. 

 40 G, p. 616). The walls give a reaction for chitin rather than for cel- 

 lulose (Harder, 1939a, 1939b; Nabel, 1939; Ritchie, 1947; Frey, 1950). 

 They are lacking in Coelomomyces, although a filamentous habit is 

 maintained (Couch, 1945b). 



The nature of the cytoplasm is changeable, differing markedly in 

 the same plant under altered conditions of environment and at various 

 ages. Often finely granular and homogeneous, it may contain dispersed 

 in it minute globules or large clodlike bodies of fatty nature. Again, it 

 may be either densely packed with irregular refractive granules or 

 reticulately or alveolately vacuolate. The cytoplasm is colorless except 

 in the male gametangia, in the immature resting spores of certain species 

 ofAllomyces, and in the sporangia of A. moniliformis and in Catenomyces. 

 Although true cross walls are formed primarily to delimit reproductive 

 structures, in the Catenariaceae they are also developed sparingly on 

 the vegetative system. In Allomyces peculiar sievelike pseudosepta 

 which resemble true cross walls also occur at intervals along the hyphae. 



REPRODUCTION 



Nonsexual Reproduction 



Nonsexual reproduction is accomplished by posteriorly uniflagellate 

 zoospores which are formed within thin-walled zoosporangia. In Blas- 

 tocladiella stubenii and in most specimens of B. microcystogena, the 

 sporangium arises from an enlarged reproductive rudiment, which is 

 derived (as it is in such a chytrid as Rhizidium) from the swollen body 

 of the encysted zoospore (Fig. 45 A, p. 661). Other species of Blas- 

 tocladiella have a single sporangium formed at the apex of the basal 

 cell (Fig. 45 E, p. 661). Catenaria and Catenomyces possess inter- 

 calary sporangia, typically separated from one another by sterile isth- 

 muses delimited by septa (Fig. 44 A, G, I, p. 651). Blastocladia (Fig. 

 46 E, p. 680) for the most part has the sporangia sessile, whereas in 



