SOME SPECIES OF PYTHIUM PARASITIC ON WHEAT IN CANADA AND ENGLAND 1

S ummary The results of a comparative study of six species of Pythium pathogenic to wheat seedlings are presented. P. arrhenomnes, P. volutum , and P. tardicrescens n.sp., were found in both Canada and England; or, for P. graminicolum and P. torulosum [?] in England and not in Canada; and P. aristosporum . n.sp., only in Canada. The English forms were obtained from Bucks, Cambs, Kent, Herts, Berks, and Lincs, and the Canadian forms from Saskatchewan. The similarity of the English form considered as a geographic strain of P. torulosum with the form reported on wheat in Italy by Petri is pointed out. Attention is drawn to the wide geographic distribution of species of Pythium on graminaceous hosts. By the method of isolation used, it was relatively easy to obtain one or more of these fungi either from wheat seedlings grown in potted soil collected at random from virtually any field with cereals in the rotation, or from seedlings collected from the poorer looking parts of such fields. All of the parasitic species isolated belong to the group of the genus with lobulate sporangia. It is suggested that the many sphaerosporangial forms encountered may render the wheat seedlings more liable to attack by the pathogenic forms themselves. The use of fertilizers may prove beneficial.