CHYTRIDIALES 293 



sibly on C. obtusa, Gonium terras, Braun (be. cit.), Germany; Chlamy- 

 domonas pulvisculus, Hormiscia sp., de Wildeman (1890: 15; 1894: 156), 

 Belgium; Chlamydomonas dillii, Dangeard ( 1 900-1 90 le: 282, figs. 

 A-L), France; pine pollen, Gaertner (1954b: 21), Egypt, South 

 Africa. 



Braun noted that the swarmers were attacked by the chytrid zoo- 

 spores, up to twelve parasites being formed on a single host cell. 

 Eventually infected swarmers came to rest and were killed by the 

 fungus. Dangeard observed the penetration of the alga by the slender 

 germ tube of the fungus, but was unable to determine whether or not 

 this tube remained unbranched during the subsequent development 

 of the parasite. Eventually the contents of the alga were reduced to 

 an amorphous reddish mass. Although the resting spores noted by 

 Dangeard were said to be spherical, in the figures they appear rather 

 subspherical. 



Rhizophydium goniosporum, which has similar sporangia to this 

 species, differs in having polygonal resting spores, sexually formed. 

 The sporangia of the fungus identified with this species by Cook (1932a: 

 136, figs. 20-25) are too spherical for it to be R. transversum. It may 

 possibly be R. acuforme. 



Rhizophydium columnaris Canter 



Trans. Brit. Mycol. Soc, 31: 135, figs. 3-4, pi. 11, figs. 3-5. 1947 



"Thallus monocentric, epibiotic. Sporangium broadly ovoid, with 

 its longer axis parallel to the host wall; wall smooth, colourless with 

 a conical protuberance on its upper surface; large sporangia 25-63 \x 

 broad x 16-27 jx high; dwarf sporangia 8-15 \i broad x 9-13 jji high; 

 dehiscing by two broad, lateral, oppositely placed pores, very rarely 

 one apical pore. Zoospores spherical, 2.6 \l in diameter, uniflagellate, 

 with a conspicuous anterior oil globule and a darker area laterally; 

 emerging singly, movement even gliding. Rhizoidal system branched 

 arising from an indistinct main axis. Resting spore sexually formed, 

 epibiotic, spherical, 10—20 (jl, wall up to 3 [x thick, colourless, smooth, 

 with columnar bands of refractive material; central contents granular, 

 germination not observed. Male thallus epibiotic, spherical, connected 



