60S AQUATIC PHYCOMYCETES 



Allomyces they are terminally or laterally placed on hyphal branches 

 arising from the basal cell. In all species of the latter genus secondarily 

 formed sporangia may develop in basipetal succession (Fig. 40 E, G, 

 p. 616). 



In members of the order the zoospores are matured within the spo- 

 rangium and are liberated through one or more pores formed upon 

 deliquescence of the discharge papillae. Under certain environmental 

 conditions the first zoospores to emerge are surrounded by a temporary 

 vesicle (Fig. 40 E, p. 616); under others they emerge individually. In 

 Catenomyces, as in some chytrids, an endooperculum is formed (Fig. 44 

 I, p. 651). In some species of Blastocladia a peculiar peglike structure 

 which appears to be endogenously produced by the distal wall of the 

 sporangium has been found (Minden, 1916; Sparrow, 1932b). The 

 function of this plug is unknown, but Lloyd (1938) observed that it is 

 divided into an inner and an outer part and she suggests that it is the 

 inner part which gives rise to the temporary vesicle often surrounding 

 the zoospores at their emergence. Indoh (1940) considered the papillae 

 on the sporangium of Allomyces to be projections of the inner sporan- 

 gium wall. Internal proliferation of the sporangia takes place in two 

 species of Blastocladia (B. prolifera and B. sparrowii) (Fig. 46 C, p. 680). 



The zoospores of all members of the order, with the exception of 

 Blastocladiella stomophilum, are very much alike in appearance, internal 

 organization, and type of motility. Although many are spherical when 

 first escaping from the sporangium, they become ovoid during active 

 swarming. The plasma may contain a few anterior, minute, colorless, 

 or occasionally colored, globules and it always bears near the center a 

 dull-gleaming top-shaped or subtriangular structure, the so-called "food 

 body" or "nuclear cap" (Fig. 46 F). In certain species of Blastocladiella 

 and Allomyces and in Catenaria allomycis, there is also present a 

 lachrymose lateral structure ("side body") of the same refractivity as 

 the food body (Fig. 45 D, p. 66 1 ), whereas in Blastocladiella stomophilum 

 there is a ring of small oil globules (Fig. 45 I). At the point of emergence 

 of the long slender posterior flagellum of the zoospore, a bright refrac- 

 tive granule, probably the blepharoplast, is often visible. The spore 

 moves in a deliberate and relatively even fashion when swimming. 

 Pronounced amoeboid movement is frequently resorted to, particularly 



