280 AQUATIC PHYCOMYCETES 



Parasitic on moving cells of a Chlamydomonas-like alga, Fischer 

 (loc. cit.), Germany; Chlamydomonas sp., de Wildeman (1890:9), 

 Belgium;(?) Palmodictyon sp., Couch (1932: 251, pi. 15, figs. 26-35; 

 see below), United States. 



Zopf's material was found in March, while the ice was still on the 

 pond and the temperature of the water was 11°-13° Reaumer (13.8°- 

 16.3° C). Up to ten chytrids were found on a single zoospore of the 

 host. De Wildeman (loc. cit.) noted that the host cell continued to move 

 even when infected by as many as six zoospores of the chytrid. In such 

 instances, however, the sporangia of the parasite did not mature. In 

 the early stages of development the fungus had no visible effect on 

 the alga, but as the parasite matured the host lost its motility and 

 finally succumbed to the invader. 



The form described by Couch (loc. cit.) on Palmodictyon sp. differs 

 in certain essential features from that of Zopf. Its sporangia are smaller 

 (6.2-9 \x in diameter) and the discharge papilla, which may be sub- 

 apical or even lateral, is much broader and longer (up to one half 

 as long as the diameter of the sporangium). Furthermore, certain spo- 

 rangia formed zoospores about one half the size of those formed by 

 other sporangia. Couch (loc. cit.) considers the organism to be inter- 

 mediate between Rhizophydium acuforme and R. minutum Atkinson. 



Grove (1917) recorded this species from Great Britain on Chlamy- 

 domonas intermedia, but Canter (1953) questioned the identification, 

 because the rhizoidal system of the fungus differs slightly from that 

 of Zopf's form. 



Rhizophydium minutum Atkinson 

 Bot. Gaz., 48: 328, fig. 4. 1909 



"Zoosporangia obpyriform or flask-shaped, broadly papillate, 5-6 \l 

 in diameter, sessile with a few slender rhizoidal filaments at the base 

 in the host cell. Apex opening by a single pore. Zoospores two to four 

 in a zoosporangium, oval, uniciliate, with a single oil drop, 2.5 u. in 

 diameter" (Atkinson, loc. cit.). 



On Spirogyra various, Atkinson (loc. cit.), United States; Spirogyra 

 sp., Berczi (1940: 82, pi. 2, fig. 13), Hungary; pine pollen, Gaertner 

 (1954b: 21), South Africa; Spirogyra sp., Lacy (1955:209), India. 



