70 
Mycologia 
species and the demonstration of its validity. The results of these 
studies are discussed under P. Cactorum. 
9. Phytophthora Cactorum (Lebert & Cohn) Schrot. 
This species was originally described from diseased cacti in 
Europe and was later included along with other forms by De 
Bary in his Phytophthora omnivora. 
Comparative studies were made by Himmelbaur (1911) on 
three forms which might well be included in De Bary’s species. 
They were designated P. Cactorum, P. Fagi, and P. Syringae. 
The cultures of P. Cactorum were obtained from Pliyllocactus 
at Dahlern. As a result of his inoculation experiments with 
these fungi on three species of cacti he concludes that inoculation 
experiments are of very little value in delimiting species. How- 
ever the results of his inoculations, which he presents in tabu- 
lated form, are quite interesting so they are quoted in their 
entirity. 
Host 
Macroscopic 
Microscopic 
Cactorum 
Fagi 
Syringae 
Cactorum 
Fagi 
Syringae 
Echinopsis Eyri- 
esii 
Much 
affected 
Much 
affected 
± Slight 
infection 
Very 
numerous 
oospores 
Very 
numerous 
oospores 
Numerous 
oospores 
Cereus tephr acan- 
thus 
=•= Slight 
infection 
=*= Slight 
infection 
Slight 
infection 
Numerous 
oospores 
Numerous 
oospores 
Few 
oospores 
Cereus Marti - 
anus 
Slight 
infection 
Slight 
infection 
± Slight 
infection 
Numerous 
oospores 
Few 
oospores 
Numerous 
oospores 
All three forms were grown in Erlenmeyer flasks on sterilized 
carrots and in Petri dishes on various media. P. Cactorum made 
the most vigorous growth while P. Syringae was the weakest. 
He considers these forms all closely related but morphologically 
distinguishable both by conidial and oosporic characters as well 
as by the mycelium. He also expresses the opinion that Pcrono- 
spora Sempervivi Schenk is identical with Phytophthora Cac- 
torum. The results of his morphological studies are given in 
tabular form for ready comparison. 
