374 Wormald. — ‘ Brown Rot ’ Diseases of Fruit Trees . 
other two strains failed to induce this nigrescence except on fully matured 
apples inoculated some time after they had been picked and stored ; it was 
also to be distinguished from the fact that on the apples so infected it 
produced very few pustules, or in some instances none at all, while the 
strains of M. cinerea and M. fmctigena from plums readily developed 
pustules. 
During 1917 another series of experiments was carried out using the 
same strain of the Blossom Wilt fungus (which, however, had been re-isolated 
from an apple spur infected from a pure culture) and other strains of Monilia 
cinerea and M . fmctigena. In this series, Experiments Nos. 4 and 5 were 
made on apples growing on a tree in the open, Nos. 1, 2, 3, 6, and 7 on 
apples which were inoculated and kept under laboratory conditions. In 
the latter case, the fruit after inoculation was placed in a glass vessel which 
had been sterilized on the inside by a thorough cleansing with cotton-wool 
soaked in 95 per cent, alcohol. The actual inoculation consisted in making 
a small V-shaped cut through the skin, removing a particle of the tissues 
underneath, and inserting mycelium from an agar culture of the fungus, the 
skin being then turned back into position. When the resulting ‘ Brown Rot ’ 
had developed for about seven days, by which time the fungi had become 
well established in the tissues, the apples were placed under bell-jars on 
a slate slab (which had also been cleansed with alcohol), the jars being 
raised above the surface of the slab on glass supports 1 cm. in height, thus 
allowing for a circulation of the air. This method, though not excluding 
the possibility of infection by other organisms during the latter stages of 
the experiment, provided conditions less abnormal than would have been 
the case had the apples been kept in an enclosed space throughout the 
experiment, and as no other organisms appeared it is to be concluded that 
the results obtained were produced by the fungi inserted in the wounds. 
In 1917 inoculation experiments on apple flowers showed that the 
strain of Monilia cinerea obtained from a c withered tip ’ of a plum tree was 
unable to induce the Blossom Wilt condition on the flowering spurs of the 
apple ; other experiments carried out in 1918 (described in detail in the 
present paper) with other strains from plum and cherry also failed to 
produce the Blossom Wilt on apple trees. The ‘ Blossom Wilt and Canker’ 
form of Monilia cinerea is therefore distinct biologically from that occurring 
generally on the species of Prunus , and it is proposed, for convenience, to 
refer to it in describing the following experiments as Monilia cinerea forma 
mali and the form on plum and cherry as M. cinerea forma pruni. Strains 
of Monilia obtained from America have also been used, and, as these have 
certain characters in common which distinguish them from M. cinerea as 
found in Europe, 1 they will be referred to as M. cinerea forma americana. 
1 Vide Ann. Appl. Biol., vol. iii, No. 4, p. 180. 
