Wilson: Studies in North American Peronosporales 209 
foe to the American tobacco grower. However evidence comes 
from a different quarter which is not so quieting. For a term of 
years serious outbreaks of a seed-bed disease of tobacco plants in 
Australia caused much loss to the tobacco growers of the colony of 
Victoria. Material submitted to Professor Massee for identification 
was pronounced P. sordid a Berk, a very different species which is 
confined to certain genera of Scrophulariaceae. However this 
Australian record is the only one of the species being found on 
Nicotiana Tabacum. 
Peronospora minima sp. nov. 17 
Hypophyllous, forming an irregularly distributed grayish 
growth over the entire under surface of the leaf, epiphyllous dis- 
coloration apparently merely chlorotic; conidiophores straight or 
slightly flexuose, 2-10 from a stoma, short and little branched, 
150-300 X 8-10 jti, branching 1-3 or 4 times, the branches straight, 
ultimate branchlets at acute angles, axial scarcely deflected, some- 
times ultimate branchlets arise in groups of three, conic, 15-20 X 
4-6 n, occasionally the conidiophore is reduced and bears only 3 
or 4 conidia-bearing branchlets ; conidia globose, very light yel- 
lowish-brown, 28-32/1; oospores subglobose, 65-80 /*, epispore yel- 
lowish, wrinkled rather conspicuously ; oogonium rather thick 
walled, slightly larger than the oospore, somewhat flattened. 
Type, in herbarium Wilson, collected by G. Lagerheim at 
Tromso, Norway, on Saxifraga cernua L., Aug. 1895. 
This is the smallest species of the genus and stands out sharply 
not only from the other species on Saxifragaceae all of which are 
considerably larger and better developed, but from the species 
which it appears to approach closest as well. In size and method 
of branching of the conidiophores it approaches nearest to P. 
violacca Berk., while the globose conidia might suggest a relation- 
ship to some of the larger species such as P. Phyteumatis Fuckel. 
i" Hypophyllis, conidiophoris densis caespitosis, griseis ; conidiophoris rectis 
vel flexuosis, 2-10-fasciculatis, brevis, pauci ramosis, 150-300 X 8-10 ft, 1-3 
vel 4-ies ramosis, ramis rectis, ultimis conicis, 15-20 X vel conidio- 
phoris minimis, cum 3-4 conidiis; conidiis globosis, diluto-aureo-bruneis, 28—32 
n; oosporis auriis, diam., 65-80/2. 
