PERONOSPORALES 1053 



thora sporangia in water culture are further evidences of its amphibious 

 nature. (This last characteristic is shared by many, probably all, species 

 of Pythium.) Whether one can regard all species of Pythiomorpha as 

 valid members of Phytophthora must await a critical study. Meanwhile, 

 see the discussions of Sparrow (1943) and Middleton (1952) 1 . Note also 

 Blackwell's (1949) very useful clarification of the terminology employed 

 in characterizing species of Phytophthora. 



KEY TO THE AQUATIC SPECIES OF PHYTOPHTHORA 2 



Sex organs present 



Both oogonia and antheridia formed; sporangia renewed by internal 

 proliferation or cymose branching of sporangiophore or both 

 Sporangia papillate; oospore filling the oogonium; without a con- 

 spicuous globule P. gonapodyides, p. 1053 



Sporangia nonpapillate 



Antheridia always amphigynous; oospore averaging 25 u, in 



diameter P. cryptogea, p. 1055 



Antheridia mostly paragynous, occasionally amphigynous; 



oospore averaging 41 [x in diameter P. megasperma, p. 1056 



Only oogonia formed; sporangia renewed only by cymose branching 



P. fischcriana, p. 1058 

 Sex organs lacking; sporangia up to 84 u, long (av. circa 60 \x) 



P. oryzae, p. 1060 



Phytophthora gonapodyides (H. E. Petersen) Buisman 3 



Meded. phytopath. Lab. Scholten, 11:7, 1927; also reprinted as Root Rots 

 Caused by Phycomycetes, p. 7. Haarlem 1927 



(Fig. 89 D-G, p. 1055) 

 Pythiomorpha gonapodyides H. E. Petersen, Bot. Tidsskrift, 29: 391, tigs. 

 6-7. 1909. Ann. Mycologici, 8: 528, figs. 6-7. 1910. Emend. Kanouse, 

 Bot. Gaz., 79: 198, pis. 12-13. 1925. 



1 See Waterhouse (1956, 1958). 



-Pythiomorpha undulata (Petersen) Apinis (1930) is considered to be Pythium 

 undulatum Petersen. 



3 Waterhouse's paper (1958), seen too late for interpolation of her conclusions in 

 the body of the text, contains a strict interpretation of this species derived from a 

 study of the type material. It is evident that the fungus had no protruding discharge 

 papilla on the convex apex of the broadly to elongate pyriform sporangium which 

 was 43-70 x 20-32 u.. There were no evidences for repeated emergence of the zoo- 

 spores and no sexual stage. She rejects all published accounts of sex organs attributed 

 to the species. 



