180 A Blossom WIU and Canker of Apple Treea 



the winter time; pustules examined in March and April have been 

 barren or the conidia present were not viable, a condition observed on 

 the Continent by Ewert(9). Three strains of M. fructigena of which a 

 sufficient number of conidia have been measured gave dimensions as 

 follows : 



Average of 100 conidia Average of 100 conidia 

 from original source taken from cultures 

 Strains of M. fructigena of strain on steamed potato 



Strain VII, mummied apple, June ... 19-0 x 12-5 /i 19-5 x ll-5;u 



„ VIII, young plums, July ... 21-5 x 13-0 /x 20-5 x 130 m 



IX, mature apple, October ... 20-5 x 13-5 yu 200 x 12-5 ;u 



{c) American Strains of Monilia. 



As much attention has been given to the study of Brown Rot diseases 

 in America it was possible to obtain specimens and cultures from that 

 continent for comparison with those described in the preceding pages. 

 In all, ten strains have been cultivated and examined. Apples and 

 cultures were received from Dr G. B. Posey of the Oregon Agricultural 

 College, a culture (from a peach) and mummified plums from Prof, 

 L. R. Jones, Professor of Plant Pathology in the University of Wisconsin, 

 mummified plums and peaches, together with cultures prepared from 

 ascospores, from Mr W. A. McCubbin, Laboratory of Plant Pathology, 

 Ontario. Thus the ten strains were from three different hosts, viz. 

 apples, plums, and peaches, and represented three widely separated 

 regions. 



The strains are characterised by certain features common to all of 

 them but absent from the Moyiilias obtained from material collected in 

 this country. The most striking character peculiar to the American 

 form is the readiness with which it produces conidia on sterilised culture 

 media; even on prime- juice agar, as plate or as tube cultures, numerous 

 tufts of conidiophores develop, usually within three or four days from 

 inoculation. 



When growing on plates of prune-juice agar the mycelium grows out 

 to form a regular circular disc with an entire or sub-entire margin, 

 resembling the growth of M. fructigena in its rate of development and 

 general habit rather than that of our grey Monilias ; the production of 

 numerous tufts of conidiophores (often in concentric zones) in these 

 cultures serve to distinguish it from M. fructigena. 



On steamed potato the conidial tufts are grey and are usually so 

 numerous that they form an almost continuous pulverulent layer over 

 the surface. In these cultures therefore the general appearance of the 



