222 PHYTOPHTHORA PARASITICA. 



Colocasicc\ lies in the development of the sexual organs. In no other 

 Phytophthora except Ph. Colocasice has the oogonium been invariably 



found either to originate from within the antheridium or to arise 

 from a separate stalk which penetrates the antheridium and grows 

 through it. Clinton, indeed, is not certain that in Ph. Phaseoli* the 

 oogonial hypha may not sometimes penetrate the antheridium. Judg- 

 ing from his microphotograplis it seems that the oogonial stalk lies 

 within the antheridium but his earlier drawings of these oospores are 

 different from the microphotographs. Hartig 3 has found in Ph. Fagi, 

 oogonia in rare cases seated on antheridia and from his observa- 

 tions of these sexual organs, evidently mature, he supposes the base 

 of an oogonium to have blown out into an antheridium. He says : 

 " Ausnahmsweise und zwar vielleicht dann, wenn in nachster Nahe 

 des intercellulareii Oogoniums kein anderweites Mycel sich findet, 

 von dem aus die Entwickelung des Antheridiums erfolgen kann, 

 schwillt der Oognientrager unmittelbar imter dem Oogonium blasig 

 an und wird direct zuni Antheridium, wie Fig. 24b zeigt. So deute 

 ich wenigstens die zuweilen auftretenden Stellungen des Oogoniums 

 auf dem Antheridium selbst." The figure to which Hartig refers 

 bears some resemblance to our figures ; there seems therefore some 

 probability that the oogonium which he found seated on an antheri- 

 dium had arisen from within it. De Bary does not make any men- 

 tion of the type of antheridium observed by Hartig. Klebahn who has 

 recently studied Ph. omnivora (obtained from seedlings of beech), in 

 pure cultures, also does not seem to have come across such an antheri- 

 dium, for he makes no mention of it, nor does Himmelbaur in his 

 more recent researches on Ph. Fagi and Ph. cactontm refer to it. 

 But supposing what Hartig calls an hypogynous antheridium to be in 

 reality an antheridium, through which the oogonium has originated, 

 still the castor Phytophthora has other points of disagreement from 

 this fungus, besides those already found from inoculation experiments 

 and from the study of their growth on artificial cultures. Hartig, 



1 Sec footnote 6 on p. 189. 



2 Clinton, G. P. Joe. cit., 1907-190S and 1905. 

 S Hartig, R. loc. cit., p. 49. 



