CHYTRIDIALES 593 



Sporangium oval, spherical, ellipsoidal, or pyriform; zoospore with 

 numerous granules, lacking a main globule 

 Sporangium bearing a long (up to 1400 a) unbranched or 



branched discharge tube; resting spores lacking 



S. marilandicum, p. 594 



Sporangium bearing one to several short broad discharge tubes; 



resting spores abundantly formed, very deeply lobed 



S. plurilobulum, p. 595 

 Zoospores 11 13 \j. in diameter; septations and trabeculae rare or 



absent S. macrosporum, p. 595 



Septochytrium variabile Berdan 



Amer. J. Bot., 26: 461, fig. 2. 1939 



(Fig. 37 C, p. 598) 



"Zoosporangia hyaline to pale brown, spherical, 4-150 u, in diameter 

 (often 75-150 \x, average 45-60 \x) with a very short, broad papilla or 

 neck, ovate, egg-shaped, broadly pyriform, 10 x 15 y. — 180 :■ 220 u. 

 (commonly 100 x 150 u.) with neck 4;jl-60[x wide, obclavate to flask- 

 shaped, 2 x 6 — 35 x 360 [j., bell-shaped, irregular, flattened and de- 

 pressed with one (rarely several) broad exit papilla or neck of varying 

 diameter and length; zoosporangia delimited by true septa at maturity, 

 sporangial wall smooth when young, striated or layered at maturity, 

 wrinkled when empty; orifice of operculum circular, 1-16 u, in diameter, 

 oi- slightly oval, 4 x 6 — 6 x 10 u.. Zoospores hyaline, spherical to oval, 

 4-6 |jl, with a single refractive globule, .7-3 u. (usually 2[x) in diameter; 

 cilium 30-45 u. long. Rhizomycelium coarse, extensive (20 u. — 1 cm.), 

 richly branched, with constrictions and septations or trabeculae extend- 

 ing partially or entirely across the rhizoids; inserted on the sporangia 

 at 1-12 points; diameter at point of insertion .4-10 u.. Intercalary swell- 

 ings usually persistent as empty or partially empty enlargements of the 

 rhizomycelium but often becoming enlarged and transformed into 

 secondary or tertiary zoosporangia or into resting spores, occasionally 

 acting only as a very large, primary centre of organization of the thallus 

 and sometimes seeming to divide into 2 cells one of which enlarges and 

 becomes a zoosporangium or resting spore while the other remains as 

 a sort of apophysis. Treatment with chlor-iodide of zinc giving a pro- 

 nounced violet colour in the sporangial walls and intercalary swellings. 



