Wilson : North American Peronosporales 
59 
Infection experiments by Sawada on various species of Colo- 
casia and Alocasia gave negative results except on forms of C. 
antiquorum. At Pusa infection experiments gave negative results 
on Fagopyrum, Jasminum, Lepidium, Nicotiana, Oenothera, 
Opuntia, Ricinus, Salpiglossis, Schisanthus , Solanun Melongena. 
and Syringa. A young potato plant showed a definite infection 
and a wounded tomato seedling gave a very indefinite infection. 
The only thoroughly successful inoculations were those on seed 
lings of Gilia nivale. The results are not surprising as an 
extention of hosts would naturally be looked for among the 
nearer relatives of the host, the Monocotyledons. 
3. Phytophthora Arecae (Colem.) Pethyb. 
This fungus, which was first described by Coleman (1910) as 
P. omnivora Arecae, is the cause of a very destructive disease of 
the Areca palm in southeastern India. It attacks the young nuts 
and the inflorescence covering them with a dense mycelial growth 
and causing the nuts to drop prematurely. Occasionally the 
entire tops of the trees are attacked, the hyphae even penetrating 
the vascular bundles. 
The hyphae vary greatly in size up to 8-9^ in diameter and 
bear a very few haustoria which are filiform and simple or rarely 
branched. More commonly there are no haustoria. The conid- 
iophores are distinctly cymosely branched. The conidia vary 
considerably both in size and shape, measuring 20.6-45.4 X 30.1- 
yi.OfjL. It appears that light is an essential factor both in the 
production and the germination of the conidia. The zoospores 
are about 11.3 X 8//,, with the anterior cilium measuring 20.7^ in 
length and the posterior one 29 fi. The oospores have not been 
observed in nature, but were produced on inoculated nuts in the 
laboratory. The antheridia and oogonia are described as being 
borne on separate branches of the same thread, the antheridium, 
at least in some cases, being formed first. The process of 
oospore-formation is said to be similar to that described by De 
Bary for P. Omnivora and by Clinton for P. Phaseoli. While it 
is scarcely credible in the light of our present knowledge of the 
subject that this species really combines the processes of oospore 
formation which are present in the species just mentioned, the 
