CHYTRIDIALES 329 



much branched, arising from a single main axis at the base of a spheri- 

 cal, 8 [i. in diameter, subsporangial, endobiotic apophysis; zoospores 

 ellipsoidal to nearly oblong, 3.3 by 2.2 \l, with several minute, basal, 

 colorless, refractive granules and a long posterior flagellum; resting 

 spores not observed. 



Parasitic on encysted Euglena sp., United States. 



Superficially resembling Rhizidiomyces apophysatus (p. 754), in the 

 possession of a long discharge tube, but differing from it in the nature 

 of its zoospores. 



Phlyctochytrium hallii Couch 

 J. Elisha Mitchell Sci. Soc, 47: 253, pi. 16, figs. 40-51. 1932 



"Sporangia sessile, one to many on the host cell, often growing on 

 the end of the cell; spherical, with a smooth rather thick wall; vari- 

 able in size, when mature 10-40 \x thick, usually 20-25 \x thick. Spo- 

 rangia with a bulbous base which may be as large as 5 < 10 \x; bulbous 

 base sometimes apparently absent. From the base a very conspicuous 

 rhizoidal system arises. Spores formed as in Rhizophidium. Spores 

 emerging through a large conspicuous pore, after which the spores 

 slowly free themselves from the mass. The process of spore discharge 

 strikingly resembles that of R. sphaerocarpum as figured by Zopf 

 (1884). Spores 2.1-4.2 jx thick, with a glistening droplet and one poste- 

 riorly directed cilium. Spores darting here and there with great rapidity. 

 Resting cells thick-walled, bluntly spiny, with vesicle from which rhi- 

 zoids arise, no small accompanying cell seen" (Couch, loc. cit.). 



On Spirogyra sp., Couch (loc. cit.), United States; Chara fragilis, 

 Ookubo (1954: 60, fig. 47), Japan. 



During the process of infection the inner wall of the alga is de- 

 pressed by the penetration tube. As development of the chytrid pro- 

 ceeds the chromatophores of the host lose their spiral arrangement 

 and collapse toward the parasite. Eventually, the pyrenoids are broken 

 up, the starch disappears, and the chloroplasts become bluish green 

 and finally brown. Discharge of the zoospores regularly occurs in 

 the late afternoon or early evening. 



