H. Worm A LI) 178 



expand, while in the blossom wilt caused by the fungus the effect is 

 not noticeable until about a fortnight after the flowers open. 



The disease has by some growers been attributed to late frosts; 

 inoculation experiments (described later in this paper) carried out in 

 a greenhouse show conclusively that the fungus readily produces the 

 wilt in the absence of frost. 



It would seem that the diseased twigs and branches bear a close 

 resemblance to those attacked by "Fire-Blight" {Bacillus amylovorus) 

 in America. Prof. H. H. \^(^hetzel, Professor of Plant Pathology in the 

 Cornell University, U.S.A., when he visited Wye College a few years 

 ago, saw trees badly cankered by Monilia, and informed us that the 

 general appearance of the diseased branches was indistinguishable from 

 the condition induced by the attacks of the Bacillus, and, as already 

 pointed out, Aderhold at first attributed the "Zweigdlirre"' of apple 

 trees to the "Fire-Blight" organism. In this connection it may be 

 mentioned that dead apple twigs examined by Prof. Worthington E. 

 Smith (20) during the winter of 1898-9 were pronounced by him to have 

 been killed by "Fire-Blight" since bacteria were found in the dead 

 tissues. No conclusive evidence that Bacillus amylovorus occurs in this 

 country has yet been published, and as old spurs killed by Motiilia 

 often contain bacteria in abundance, it seems probable that Prof. W. E. 

 Smith was mistaken in his diagnosis and that the specimens seen by 

 him were twigs killed by Brown Rot. 



IV. The Blossom Wilt Fungus compared with other 

 Mo.xiLiAS OF Fruit Trees. 



(a) Cultural studies of Monilias found in this country. 



While circumstantial evidence obtained during observations made 

 in the open made it very probable that the Monilia found on the spurs 

 and cankers produced infection of the flowers, for confirmation of this 

 it was necessary to reproduce the disease by the inoculation of flowers, 

 using pure cultures. The organism has therefore been cultivated on 

 sterilised media, and' the cultures obtained have provided a means of 

 comparing this with other forms of Monilia with respect to certain 

 characters appreciable only in pure cultures. 



Some thirty strains of the fungus have been cultivated in pure culture, 

 many of them in dupUcate, and, without exception, no constant differ- 

 ences could be detected in the various strains. Two methods of obtaining 

 the cultures have been adopted. When the fungus is found in the 



Ann. Biol, in 12 



