CHYTRIDIALES 297 



Sporangium narrowly ellipsoidal to cylindrical, 48-54 jx high by 17- 

 22 [a in diameter, wall thin, smooth, colorless; rhizoids branched, 

 arising from a stout main axis which is slightly expanded just beneath 

 the host wall; zoospores spherical, pale rose-colored, 3.25-4 \x in diam- 

 eter, with an oil globule, escaping through a wide apical pore; resting 

 spore spherical, 21-31 \x in diameter, with a thick smooth brownish- 

 red exospore, forming zoospores upon germination. 



In Cladophora, Italy. 



The slight inflation of the subsporangial part of the main rhizoidal 

 axis is not of sufficient import to warrant transference of the species 

 to Phlyctochytrium. From the figure, the resting spore upon germination 

 appears to have cracked open and emitted the spores through a wide 

 aperture. 



Rhizophydium hyalobryonis Canter 



Ann. Bot. London (N.S.) 15: 148, figs. 12, 13. 1951 



(Fig. 10 C, p. 108) 



"Thallus monocentric consisting of a sporangium and branched 

 rhizoidal system. Sporangium cylindrical, 4.5 [x high x 2.5 [i broad to 

 15.5 u. high x 5.0 u, broad, usually with its long axis set at right angles 

 to that of the host envelope. On dehiscence the apex of the sporangium 

 dissolves and from 6 to 18 zoospores emerge. Zoospore spherical, 

 2.5-3 [X in diameter with a refractive globule and single posterior 

 flagellum. Resting spore cylindrical, oval, or bean-shaped, 4.5 jx high 

 X 3 [x broad to 9.5 jx high x 4.5 [i broad; wall, smooth, colourless, 

 content composed of several small refractive globules. The resting 

 spore is formed after fusion of the content of a small male 2.3 [x diam- 

 eter, with a larger female cell. The empty male cell remains adherent 

 to the mature resting spore. Germination not observed" (Canter, 

 he. cit.). 



Parasitic on the planktonic alga Hyalobryon polymorphum, Great 

 Britain. 



In early stages of development of the parasite the flagella of the alga 

 are still motile. 



