BLASTOCLADIALES 623 



Explanation of Figure 41 



A-J. Allomyces javanicus Kniep: A, immature zoosporangium, some of 

 whose nuclei are dividing; B, tangential section of more mature sporangium 

 showing cleavage furrows in center; C, two zoospore initials, each bearing a 

 single nucleus; chromatic material which will eventually become aggregated 

 around nucleus to form conspicuous nuclear cap has appeared in cytoplasm ; 

 D-E, further stages in concentration of nuclear-cap material; F, mature zoo- 

 spore showing large nuclear cap, granular nucleus, and small deep-stained 

 nucleolus, which is connected by a delicate thread to a minute peripheral 

 blepharoplast, to which, in turn, the single posterior flagellum is attached; 

 sequence of formation of nuclear cap and internal organization of swarmer 

 are the same in all the swimming bodies (i.e. zoospores, gametes, etc.) in 

 Allomyces; G, very young sporophyte plant showing portion of first-formed 

 rhizoids at base and, at tip, germ tube which will produce hyphae; contents 

 are strongly vacuolate and bear two resting nuclei and a dividing one; H, 

 hyphal tip forming rudiment of resting spore ; note characteristic vacuolization ; 

 1, very early stage in germination of resting spore; abundant chromatic 

 material characteristically found in cytoplasm of resting spore prior to incep- 

 tion of germination has by now almost disappeared; /, germinated resting 

 spore showing enlarged sporangium which has burst resting-spore wall, and 

 nearly mature planonts ; latter are in same stage of maturation as are the two 

 zoospores in D. K-O. Allomyces neo-moniliformis Indoh; K, germinating rest- 

 ing spore; note that here, in contrast to J (A. javanicus), protoplasm has been 

 cleaved into segments bearing from one to several nuclei; L, germinated 

 resting spore with cysts bearing from one to several nuclei; M, "primary R. 

 S. zoospore," bearing three nuclei; nuclear cap has disappeared; according to 

 McCranie, these zoospores bear no flagella; N, segregation of "secondary 

 R. S. zoospores," showing usual aggregation of chromatic material around 

 nucleus; O, stages in fusion of swarmers (isogamous gametes) liberated from 

 cysts to form biflagellate zygote, which gives rise to new sporophyte plant. 

 P. Allomyces javanicus Kniep, gametangia showing nuclei in terminal male 

 and subterminal female arranged around periphery. Q-V. Allomyces arbuscula 

 Butler: Q, female gamete stained with Janus green; with the exception of 

 deep-staining lipoid granules in cytoplasm surrounding nucleus and nuclear 

 cap, structure is like zoospore shown in F; R, stage in conjugation of male 

 (small) and female gametes; here nuclei are coming to lie side by side 

 without nuclear cap material (dark) between them; S, planozygote with two 

 nuclei, as yet unfused, and fused nuclear caps; T, resting zygote; flagella have 

 been lost; U, zygote in which nuclei are beginning to fuse, the nucleoli still 

 being distinct; nuclear cap has almost completely dissociated; V, germinating 

 zygote in which fusion of nucleoli is complete. 



{A-P, McCranie, in Sparrow, 1943; Q-V, Hatch, 1938) 



