BLASTOCLADIALES 667 



liberate spores, 7 x 9 jjl, through several papillae. Submerged in water, 

 on the usual ill-defined natural substrata, or under crowded conditions 

 on agar media, R. S. vary from 18 to 170 pi diameter, with or without 

 pits, or with pits confluent in irregular depressions, and with degree of 

 pigmentation varying from light yellow to deep brown; stalk may be 

 pyriform or cylindrical; in liquid culture often with 1 to 4 septa below 

 sporangium. Ca. 99% of plants derived from R.S. spores bear apical 

 reproductive units which are thin-walled, colorless and spherical to 

 ovoid-pyriform, with constant dimensions under controlled conditions 

 on agar media, but with great variation in size and shape on natural 

 substrata. Swarmers, mostly 7 9 ;j., discharged through one to several 

 papillae. Ca. 1 % of R.S. spores yield thin-walled plants bearing apical 

 reproductive units with orange pigmentation, similar to those of color- 

 less plants in shape and size, but swarmers are 4 x 6 \i. No one type of 

 swarmer is capable of fusing with any other. On media containing bicar- 

 bonate, ca. 95-100% of R.S. spores give rise directly to R.S. plants 

 rather than thin-walled plants" (Cantino and Hyatt, he. cit.). 



On silica-gel agar, submerged in fresh- water pond, United States. 



Blastocladiella stomophilum (Couch and Cox) Couch and Whiffen 



Amer. J. Bot., 29: 587. 1942 

 (Fig. 45 H-I, p. 661) 



Clavochytridiitm stomophilum Couch and Cox, in Cox, J. Elisha Mitchell 

 Sci. Soc, 55: 390, fig. 1, pis. 45-46. 1939. 



"Thallus monocentric; each thallus at maturity consisting of a coarse 

 intramatrical rhizomycelium and an extramatrical zoosporangium. 

 Rhizoids more or less profusely branched, sometimes constricted or 

 ovoid, ellipsoid or cylindrical, sessile or stalked, the length of the stalk 

 variable (up to 320 \x). Spores escaping singly from one or more exit 

 papillae, remaining motionless or becoming amoeboid for a few seconds 

 at the mouth of the sporangium and then swimming away. Spores 

 posteriorly uniciliate (length of cilium 35 to 50 a), 3.5 x 6.5 \x, ovoid or 

 elliptical, with two to twelve small eccentric refractive bodies. Empty 

 sporangium hyaline, persisting on the surface of the dead host. Resting 

 spores unknown" (Couch and Cox, in Cox, loc. cit.). 



Saprophytic on boiled corn (maize) and grass leaves used as bait, 

 United States. 



