ON A SERIOUS DISEASE IN THE CHERKY ORCHARDS OF KENT. 313 
ON A SERIOUS DISEASE IN THE CHERRY ORCHARDS OF 
KENT. 
{Being a Beport by Mr. W. Cakruthers, F.B.S., made to, and reprinted 
by permission of the Coiuicil of the Boyal Agricultural Society of 
England) 
A LEAF disease of Cherries has lately been reported from several orchards 
in the county of Kent. In the early summer it aftects the leaves and fruit 
simultaneously, rendering the latter unfit for market. In autumn and 
winter its presence is easily detected. The diseased leaves remain 
attached to the branches as if the tree had been killed in the full vigour 
of growth, just as the withered leaves remain on a branch that has been 
severed from the stem. 
The fall of the leaf in autumn is a normal process carried out by the 
living leaf, which forms at the point of its attachment to the branch a 
cicatrix that secures when completed the easy severance of the leaf from 
the branch, leaving a clean scar. The speedy and fatal injury to the leaf 
caused by the fungus prevents the formation of this cicatrix, and the leaf 
remains attached to the tree. 
A further striking characteristic of this disease is the shortening of the 
branches which bear the diseased leaves. (Fig. 162.) The internodes or 
joints between the leaves of these branches have not been developed. The 
year's growth, which should have extended to a considerable length, 
measures less than an inch. The crowded leaf -bases have each a healthy bud 
in the axil. The dwarfing of the branch is not due to any attack from a 
fungus, for no fungus is present in the tissues. The dwarfing is entirely 
due to the want of food, consequent on the early death of the leaf. That 
this is the case is confirmed by the fact that some of the dwarfed branches 
have produced in the following year vigorous normal shoots. 
The leaves were not received until late in the year, when they were 
found to be spotted with groups of minute black fruits (perithecia) of some 
parasitic fungus. (Fig. 163.) A section through one of the groups shows 
that the proper tissue of the leaf is much disorganised, and is everywhere 
penetrated and destroyed by the brownish mycelium of a fungus connected 
with the perithecia. These perithecia are seated just below the epidermis, on 
both surfaces of the leaf, though they are found chiefly on the under surface. 
They are in some cases dead and their contents dispersed, in others there 
is a compact mass of colourless fungal tissue inside the dark outer skin ; 
this may be the dormant condition of the fungus. Sections through the 
leaf-stalk show also a very luxuriant growth of the mycelium, which is 
confined to the cortical tissue. It is very irregular in form and pushes its 
way between the cells. It does not extend beyond the petiole, stopping 
short at the point where the large cortical cells of the petiole are in con- 
tact with the small round compact cells of the twig, into which the fungus 
does not penetrate. 
The disease has been spreading rapidly in Kent during the last few 
