PERONOSPORALES 



209 



and laterally biciliate. After encyst ment the spore may emerge 

 and undergo a second period of motility. Oogonia and oospores 

 resembling those of Phytophthora are described by Kanouse. The 

 oospore is sometimes developed parthenogenetically. Antheridia , 

 when present, are paragynous. Although the irregular hyphae, 

 proliferating sporangia, repeated swarmspore emergence, and 

 saprophytic and aquatic habit are characters not outstanding 

 in all species of Phytophthora they occur individually in various 

 species of the genus. There seems to be no tangible basis for 



Fig. 73. — Phytophthora gonapodioidis (Petersen) Buisman. (a) Nested 

 aspect of sporangia resulting from proliferation, {h) Secondary sporangium 

 formed beyond primary, the inner wall of the latter having been pulled upward, 

 (c) Delimitation of swarmspores. (d) Swarmspore. (e) Mycelium. (After 

 Kanouse 1925.) 



separation of the two genera. The species has been transferred 

 to Phytophthora by Buisman. Recently Apinis (1930: 234) 

 has transfered Pythium undulatum Petersen to Pythiomorpha. 



The genus Siigeosporium West (1916; 1917) based on S. marat- 

 iiacearum West, having a mycorrhizal relation with certain ferns, 

 is as yet imperfectly understood. Though regarded by its author 

 as related to Phytophthora it seems to be, in fact, wholly dissimilar. 

 The peculiar thick-walled resting spores figured by West recall 

 those of Blastodadia and AUomyces. 



4. Trachysphaera Tabor & Bunting (1923) 



This extremely interesting genus was recently founded on a 

 single species, T. fructigena Tabor & Bunting (Fig. 74), cause 

 of a disease of cocoa and coffee fruits in the Gold Coast Colony 

 in Africa. The sexual stage is similar to that of the //i/e.sta//.s' 

 group of Phytophthora. The antheridium forms a collar about 

 the base of the oogonium, but the latter is ornamented with 



