H. WORMALD 



183 



this country. The mode of growth on culture media is also similar to 

 that of our grey Monilias. Neither of the strains from Holland has 

 produced definite brown zones in tube cultures of prune-juice agar but 

 irregular brown patches eventually appeared. They thus resemble 

 (and are probably identical with) a form frequently found on plums 

 and acid cherries in Kent. 



I have not yet obtained diseased apple twigs from abroad. 



{e) Nowenclafure of fhe various forms. 



In cultures it is possible therefore to distinguish four types of 

 Monilia as found on cultivated fruit trees of the genera Pyrns and 

 Prunus, as here tabulated : 



(1) Monilia fructigena, 

 occurriug commonly 

 on apples and plnms, 

 and frequently on 

 sweet cherries. 



(2) Blossom Wilt 

 Monilia of the apple, 

 also occurring occa- 

 sionally on plums. 



(3) A grey Monilia 

 frequent on plums 

 and sweet cherries. 



(4) American form of 

 Monilia. 



Prune- juice agar plate 

 cultures 



Margin almost entire or laciniate; no 

 brown coloration; conidia absent. 



Margin with deltoid or flabelliform 

 lobes, growth usually arrested about 

 mid-way between centre and side of 

 plate, and new outgrowths as flabelli- 

 form lobes develop, usually from 

 the sinuses; olive-green, to brown, 

 zones appear, the first usually at 0-5 

 to 1 cm. from the centre; conidia 

 absent. 



As above but no brown zones appear. 



Margin entire or crenate ; conidial tufts 

 numerous, usuallj' in concentric 

 circles ; brown coloration of the agar 

 absent or appears as a peripheral 

 band near edge of plate; growth 

 generally more rapid than in (2) or 

 (3) and more uniform. 



Cultures on steamed 

 potato in Roux' tubes 



Conidial tufts yellow, 

 well-developed at 

 upper end of potato, 

 forming raised zones. 



Conidial tufts grey, 

 few and scattered. 



Conidial tufts grey, 

 more numerous than 

 in (2), often appear- 

 ing in concentric 

 circles round point 

 of inoculation. 



Conidial tufts gre}% 

 almost covering the 

 whole surface in a 

 continuous layer. 



As shown in the table the successive brown zones typical of the plate 

 cultures of the blossom-wilt Monilia do not appear in cultures of the 

 other forms ; sometimes a brown coloration occurs in the plate cultures 

 of the American form but in that case it commences as a peripheral 

 band when the mycelium approaches, or has reached, the edge of the 



