CHYTRJDIALES 295 



Rhizophydium oblongum Canter 

 Trans. Brit. Mycol. Soc, 37: 116, text-fig. 3, pi. 5, fig. 4. 1954 



(Fig. 10 J-K, p. 108) 



"Thallus monocentric, eucarpic and epibiotic within the envelope 

 of the host cell. Sporangium oblong to oval, 3-7 \x wide and 7-24 u, 

 long, or subspherical 4.5-9 \x wide and 5.5-9.5 \x long, developed by 

 enlargement of the zoospore. Rhizoid consisting of a minute main axis 

 bearing a tuft of short rod-like branches. On dehiscence, sporangium 

 wall dissolves at one or both ends and owing to its delicate nature 

 becomes invisible. Zoospores 2.5 \x (20-60 in a sporangium), oval 

 when swimming, with flagellum and oil globule anterior but former 

 directed backwards. Resting spore oval to subspherical, 5-9 \j. long 

 and 4-6 \i broad, with a thick, smooth wall and containing several 

 small globules. Resting spore formation preceded by fusion of un- 

 equal gametes; male attached directly or by means of a conjugation 

 tube (up to 5 [x long) to the female. Germination unknown" (Canter, 

 be. cit.). 



Parasitic on Dinobryon spp. in plankton; D. diverge/is, D. stipitatum, 

 Canter (loc. cit.), Great Britain; Dinobryon sp., coll. V. Tonolli, 

 Canter (be. cit.), Italy; coll. A. Lundh, Canter (be. cit.), Sweden. 



The parasite rests between the lorica and protoplast of the host, 

 and a feebly developed rhizoidal system penetrates the latter. The 

 algal cell ; s at first only slightly affected, since its fiagella continue 

 to move even when a large sporangium of the parasite is maturing on it. 



Further observations on the structure of the zoospore are needed. 

 If, as Canter states, confirmation is obtained of the anteriorly attached, 

 posteriorly directed flagellum, transfer to another genus may be nec- 

 essary. It is possible that many other "posteriorly uniflagellate" chy- 

 trids have a similar attachment of their flagellum. 



Rhizophydium goniosporum Scherffel 

 Arch. Protistenk., 53: 20, pi. 1, figs. 40-42, pi. 2, figs. 43-50. 1925 



(Fig. 17 U-V, p. 228) 



Sporangium sessile, broadly citriform or broadly ovoid, occasionally 

 irregular, with a slightly flattened upper surface, its long axis parallel 



