Wormald ’ — ‘ Brown Rot ’ Diseases of Fruit Trees. II. 169 
described under those names by various authors, but until this relationship 
is established experimentally the present writer prefers to retain the name 
Monilia cinerea , Bon., for the grey Monilia occurring parasitically in Europe 
on the commonly cultivated species of fruit trees of the genera Pyrus and 
Primus. 
Summary. 
(1) In Britain there are two species of Monilia parasitic on fruit trees 
of the genera Pyrus and Primus , viz. M. fructigena , Pers. = Sclerotinia 
fructigena (Pers.), Schrot., and M. cinerea , Bon. 
(2) The two species are to be distinguished by — 
(a) the colour and size of the pustules, 
(b) dimensions of the conidia, 
(c) mode of growth on sterilized culture media, 
(d) mode of branching of germ tube of conidium, 
(e) mode of parasitism. 
(3) M. fructigena causes a fruit rot of apples, plums, and cherries, and 
on apple trees may produce cankers by invading the branch through the fruit. 
M. cinerea occurs on apple, plum, and cherry trees and causes diseases 
as follows : 
Apple trees — ‘ Blossom Wilt and Canker ’ disease. 
Plum trees — fruit rot, blossom wilt, cankers, and a ‘ Wither Tip 5 
disease of young shoots. 
Cherry trees — fruit rot, blossom wilt, and may kill twigs by 
entering through the flowers. 
(4) In M. fructigena conidia production is inhibited during winter ; 
M. cinerea , on the other hand, begins to develop new pustules about the 
beginning of December and produces conidia freely during winter and spring. 
(5) The winter conidia of M. cinerea are considerably smaller than 
those produced by it in summer. 
(6) The form of M. cinerea parasitic on apple trees is biologically and 
physiologically different from the form found on plum and cherry trees : 
M. cinerea forma mali produces a blossom wilt of apple trees ; 
it readily secretes an enzyme which oxidizes tannins. 
M. cinerea forma pruni , when apple flowers are inoculated with 
conidia, attacks only the flowers actually inoculated and does 
not invade the axis of the inflorescence ; it secretes the oxidiz- 
ing enzyme far less freely than the apple form. 
(7) The oxidizing enzyme is secreted freely by M. cinerea f. mali when 
growing in — 
(a) liquid culture media, 
(b) infected apples, 
(c) infected apple spurs. 
