552 Scientific Proceedings, Royal Dublin Society. 



named was supplied to me by tlie Bureau jMicr la dish'ibution de cultures de 

 inoismures of the International Association of Botanists, in Amsterdam, 

 with the information tliat it was supplied by Dr. Rutgers, of Buitenzorg, 

 from an isolation by Jensen, but that no description of it had yet been 

 published, and that probably it was identical with P. Nicotianae de Haan. 



In the case of certain of tliese species such as P. Colocasiae the sexual 

 organs are still unknown, in the case of P. infeslans they have only recently 

 been discovered (6), while in P. Faheri, although oospores have been found, 

 the mode of their development has not been followed in detail. 



Taking into account only the vegetative and asexual reproductive 

 characters of the fungus causing the Pink Eot of the potato, it would 

 certainly appear to be a species of Phytophthora, but the characters of the 

 sexual organs would seem to place it in a position not_only outside of that 

 genus, but also outside of any of the hitherto described families of the 

 sub-class Oomycetes. 



It therefore seemed highly desirable that these characters should be 

 compared with those of as many species of Phytophthora as possible, both by 

 means of the publislied descriptions as well as by studies where feasible on 

 living material. 



Thanks to tlie kindness of Professor Klebahn, I have been fortunate in 

 obtaining cultures of P. Si/ringae, P. Fagi, and P. Cactorum, which, according 

 to Himmelbaur (13), are three distinct species, or at least "physiological 

 races," possessing distinctive morphological characters ; and in what follows 

 I have treated P. Fagi and P. Cactorum as distinct species, although the 

 former is not included as such in the list of species enumerated above. 

 P. Syringae is certainly distinct. Dr. Clinton was good enough to provide me 

 with a culture of P. Phaseoli, while from the above-mentioned Bureau I have 

 obtained cultures of P. Cactorum, P. Faberi, P. Nicotianae, and P. Jatrophae. 

 With regard to P. Faheri, I have not yet succeeded in getting it to produce 

 either sexual organs or conidia ; and the studies of P. Nicotianae and 

 P. Jatrophae are not yet sufficiently advanced for any proper comparisons to 

 be made, the cultures having been obtained only very recently." 



The development of the sexual organs has been followed in cover-glass 

 film cultures in the cases of P. Cactorum and P. Fagi, and found to agree with 

 the accounts already published. Up to the present I have only succeeded in 

 obtaining the sexual organs of P. Si/riiigae in the interior of pieces of sterile 

 carrot, where, of course, their development could not be followed, but the 

 final stages agree with those described by Klebahn, and it is safe to assume 



See Addendum to this Paper, p. 560. 



