478 AQUATIC PHYCOMYCETES 



important and distinctive feature of the fungus upon which the genus 

 is based, namely, the simultaneous formation of two different types of 

 sporangia on the same thallus. Although the specific diagnosis describes 

 the sporangia as "smooth to tuberculate," the text, summary, and 

 figures all indicate that they are either smooth or tuberculate and that 

 both kinds occur together. 



Ajello (1948a: 9) considered the possibility of the affinity of his 

 fungus to the Blastocladiales and concluded that even though there are 

 marked blastocladiaceous features, the lack of a side body and the 

 monopolar method of germination offer stronger evidence for placing 

 Polychytrium in the Chytridiales. 



POLYCHYTRIUM AGGREGATUM Ajello 



Mycologia, 34: 443, figs. 1-16. 1942 



"Rhizomycelium extensive, coarse, tenuous portion, apart from rhiz- 

 oids, 2-12 \l in diameter, profusely branched, occasionally septate, hya- 

 line at first, becoming yellowish-brown at maturity. Zoosporangia in 

 aggregates of two or more, terminal and intercalary, non-apophysate, 

 hyaline at first, becoming yellowish-brown at maturity, wall .7 \x thick; 

 smooth to tuberculate; spherical, 14 < 29 \x; ovoid, ellipsoid, 12-20 X 

 22-40 [x; clavate, obclavate, 12-24 x 29-102 \i; pyriform, obpyriform, 

 elongate, cylindrical, 8-25 x 17-75 \i\ tubercles on sporangia up to 

 7 (J. wide at the base and 5.5 \l in height; exit pore or tube varying in 

 length, diameter 3.5 \x\ proliferating, exit tube of secondary or tertiary 

 sporangia often penetrating the primary sporangia! wall. Zoospores 

 delimited within the sporangium, emerging and forming a motionless, 

 spherical mass at the mouth of the exit pore; spherical 4.4-5.5 \l with 

 a conspicuous, large, lunate opaque region, 1.5-2 x 3-3.5 \i, surrounded 

 by several opaque granules, no conspicuous single refractive globule 

 present; flagellum 24—29 \x long. Resting spores unknown or doubtful" 

 (Ajello, be. cit.). 



Saprophytic in decaying vegetation in bogs, chitinous substrata, coll. 

 Karling, Ajello {he. cit.), Brazil; chitin (Michigan), United States. 



Ajello made a cytological study of the species (1948a, see p. 101) and 

 a nutritional one (1948b). Both were based on an isolate from Brazilian 



