The ‘Brown Rot’ Diseases of Fruit Trees, with Special 
Reference to two Biologic Forms of Monilia cinerea. 
Bon . 1 II. 
BY 
MAY 3 1920 
H. WORMALD, M.Sc. (Lond.), A.R.C.Sc. NJj, 
Mycological Department , South-Eastern Agricultural College , Wye , Kent. 
MuS®> 
With Plates IV and V. 
Contents. 
PAGE 
I. Introduction • 143 
II. The Secretion of an Oxidizing Enzyme by Monilia cinerea . . . .144 
(a) In Liquid Culture Media 144 
(3) In Infected Apples 153 
( c ) In Infected Flowering Spurs of the Apple 154 
III. Morphology and Taxonomy of the ‘Brown Rot’ Fungi .... 159 
(a) Colour and Size of Pustules ...... 159 
( b ) Dimensions of Conidia 160 
(1 c ) Viability of Conidia . . 163 
(a) Cultural Studies 164 
(e) American Strains of Monilia 165 
(f) Taxonomy . 166 
IV. Summary 169 
I. Introduction. 
I N Part I of this article it was shown that the c Brown Rot ’ diseases of 
fruit trees in this country are caused not only by Monilia fructigena , 
which has been generally assumed to be the species responsible for all such 
diseases in Britain, but also by M. cinerea , the latter having been found, in 
many cases, to be more destructive than M . fructigena ; the two species are 
to be recognized by their morphological characters and by their mode of 
parasitism. Further, it was pointed out that the morphological species 
M. cinerea includes two f biologic ’ forms distinguished by the degree of 
virulence when apple flowers are inoculated with their conidia ; one form, 
found on infected flowering shoots and cankers of apple trees, is able to 
1 This article is included in a Thesis approved for the Degree of Doctor of Science in the 
University of London. 
[Annals of Botany, Vol. XXXIV. No. CXXXIV. April, 1920.] 
