The ‘Brown Rot’ Diseases of Fruit Trees, with Special 
Reference to Two Biologic Forms of Monilia cinerea. 
Bon. I. 
BY 
H. WORMALD, M.Sc. (Lond.), A.R.C.Sc. 
Mycological Department , South-Eastern Agricultural College , Wye , Kent. 
With Plates XXV and XXVI. 
Contents. 
PAGE 
I. Introduction .361 
II. Historical 363 
III. General Observations . 367 
(ci) The Occurrence of Monilia fructigena and M. cinerea on Primus spp. . . 367 
(d) The ‘Wither Tip’ Disease of Pium Trees in 1918 ...... 368 
(c) Sources of Infection on Plum Trees ......... 369 
( d ) An Epidemic Outbreak of a ‘ Blossom Wilt’ of Plum and Cherry Trees in 1918 369 
(e) M. cinerea and M. fructigena on Pyrus spp . . 370 
IV. Methods adopted in isolating Pure Strains 371 
V. Inoculation Experiments with M. cinerea and M. fructigena : 
(a) Apples inoculated with Strains of the Two Species 373 
(P) Plums ,, „ „ „ „ 381 
(V) Plum Flowers inoculated with Strains of M. cinerea . . . . *387 
(a) Apple „ „ „ „ „ „ 389 
VI. Conclusions 397 
I. Introduction. 
I T has long been common knowledge among horticulturists and plant 
pathologists that the fruits of the cultivated species of the genera Pyrus 
and Primus are frequently attacked by fungi which, gaining access to the 
nutritious parenchymatous cells of the fruit through wounds or abrasions of 
the skin, rapidly develop within the tissues. The progress of the disease is 
indicated by a discoloration of the affected cells, the resulting brown colour 
often showing a striking contrast with the healthy tissues, particularly in 
the case of immature fruit with pale green skins (see Fig. 4). 
[Annals of Botany, Vol. XXXIII, No. CXXXI, July, 1919.] 
