Wilson : North American Peronosporales 
67 
tinted, and there are some that seem to grade into P. Phaseoli; 
or at least are not very different from that species, as the oogonial 
walls are only slightly tinted and thickened.” These hybrid 
oospores were produced from the oogonia of P. infestans and 
the antheridia of P. Phaseoli, and measure about the same as the 
normal oospores of P. infestans. The average measurements of 
P. Phaseoli are 22.5 /«. and of P. infestans and the hybrids are 
about 30 jx. The evidence of the hybrid nature of these oospores 
appears to be very strong. It would be interesting to know 
whether they produced fertile hybrids and if so if they are Men- 
delian or non Mendelian in their behavior. 
Hybrids with P. Cactorum are also reported but are said to be 
much more difficult to produce. It is unfortunate that no host of 
this last species is given, as in the light of recent work on the 
genus it would be interesting indeed to know what strain of this 
species was used for the experiments. 
Much attention is devoted by Jones to what may be called in a 
broad sense physiological problems, such as the relation of the 
fungus to its host, to culture media, to temperature, etc. Much 
of this data has been published previously and so need not be dis- 
cussed at present except in a very general way. His observation 
(p. 28) concerning the production of conidia within the host is 
apparently the first reference to this habit in the genus Phytoph- 
thora. The subject of resistant varieties is discussed in con- 
siderable detail. “ Well-marked and fixed differences exist 
among potato varieties in relative susceptibility to invasion by 
Phytophthora infestans. . . . These differences occur in foliage 
as well as in tuber. While foliage and tuber resistance generally 
go together, this relation is not invariable. The disease resistant 
quality is resident in large measure, and probably wholly, in the 
interior tissues of both leaf and tuber. In the tuber it is uni- 
formly distributed throughout the flesh ” (p. 83). 
In discussing the hosts of this species reference is made to the 
list given by De Bary which includes “ not only a number of 
other species of Solanaceae grown in gardens, but that he has 
observed it on one of the exotic species of the Scrophulariaceae, 
Schisanthus grahami, and that Berkeley has described a case 
where it occurred on another one of the same group, Anthocercis 
