SAPROLEGNIALES 831 



Thraustochytrium proliferum Sparrow 



Biol. Bulletin, 70: 259, text figs. 22-28, pi. 1, fig.2. 1936 



(Fig. 60 D-F, p. 806) 



Sporangium sessile, obpyriform, 15.6-18 \l high by 10-13 \i in 

 diameter, very thin-walled, smooth, colorless; rhizoid branched or 

 unbranched ; zoospores few, somewhat angular at liberation, later more 

 spherical, 4 \x in diameter, when motile gibbose-pyriform and 3 ;x 

 long by 2.5 \x wide, with an anterior refractive colorless granule and 

 two flagella, movement an even swimming; resting spore not ob- 

 served. 



Saprophytic on Bryopsis phunosa, Ceramium diaphanwn, United 

 States. 



The zoospores are strongly attracted by the disintegrating chlorophyll 

 of the Bryopsis and swarm around the outside of the portions of the cell 

 containing it. As a result, dense clusters of sporangia may be formed in 

 these regions. 



Thraustochytrium globosum Kobayasi and Ookubo 

 Bull. Nat. Sci. Mus. (Tokyo), 33: 60, fig. 6. 1953 

 (Fig. 63 C-D, p. 824) 



Zoosporangia gregarious on host cell, sessile, globose or ellipsoid, 

 sometimes conic at the base, never proliferating, smooth, hyaline, thin- 

 walled, without a papilla, 5-10 \x high, 5-20 \x in diameter, containing 

 eight to twenty-four to thirty zoospores, at maturity bursting, the upper 

 half of sporangial wall irregularly torn away; rhizoid single and simple, 

 moderately long; zoospores polyhedral in the immature stage, becoming 

 nephroid at maturity, 3-4 by 2.5 \x, with two oppositely directed, 

 lateral flagella, containing two or three granules, initiating movement 

 within the sporangium; resting spore not observed. (Modified from 

 Kobayasi and Ookubo.) 



On green algae (Ulotrichales), Japan. 



Differing markedly from Thraustochytrium proliferum in the behavior 

 of the zoospores and lack of internal proliferation (see discussion under 

 the genus). 



