1 84 A B/ossom Wilt and Canker of Apj^le Trees 



plate. When growing as "slant cultures" in test-tubes both M.fructi- 

 gena and the American Monilia usually produce a browning in old 

 cultures, but this commences at the extreme lower end of the slant and 

 gradually extends for some distance upwards, white in the case of the 

 blossom-wilt fungus the first brown zone appears usually from 0-5 to 

 1 cm. from the point of inoculation when the culture is still quite young 

 (often within a week). 



The typical hyaline form from plums and sweet cherries remains 

 colourless even in old slant cultures. 



On the Continent, opinion is divided as to whether all instances of 

 Brown Rot, caused by Monilia, on fruit trees are to be attributed to 

 one species only (retaining for it the name Monilia fructicjena), or to 

 more than one. Those who favour the latter view generally assume 

 that there are three species concerned, viz. M. fructigena, said to occur 

 chiefly on the pomaceous fruits, characterised by its yellow pustules and 

 comparatively large conidia which usually are not viable in winter : 

 M. cinerea, considered to be found almost exclusively on the "stone" 

 fruits, with grey pustules and smaller conidia which retain viability 

 throughout the winter : and M. laxa, a grey form, with small conidia, 

 occurring on apricots. Aderhold and R.uhland(4) claim to have proved 

 that these three species are to be distinguished by their respective 

 ascigerous {Sclerotinia) stages, which they describe. S. fructigena they 

 obtained from mummified apples, and from the ascospores were able 

 to develop the yellow Monilia stage, M. fructigena. That the two forms 

 are stages in the life-history of one fungus appears therefore to be fully 

 established. With regard to Sclerotinia cinerea their conclusions are 

 less convincing. They were unable to obtain an ascigerous form from 

 peaches, plums or cherries, so described the form, which they refer to 

 S. cinerea, from apothecia (preserved in spirit) which had been found 

 on mummified peaches and had been sent to them from America, and 

 assumed that the Monilia cinerea of Europe is its conidial stage. 

 Mummified apricots yielded a Sclerotinia, which they described and 

 named S. laxa, with Monilia laxa as its conidial stage. 



Since, as has been shown above, the Sclerotinia generally occurring 

 in America produces a conidial stage which can be readily distinguished, 

 in cultures, not only from the grey MonUias of this country but also from 

 those strains obtained by the writer from plums received from Holland, 

 it would seem probable that Aderhold and Euhland included in their 

 diagnosis of the one species Sclerotinia cinerea two forms which are very 

 different when grown under certain cultural conditions. 



