340 Report or THE HorrircuLturist oF THE 
attacked, though the trunks and branches of the latter are some- 
times badly injured, and twigs of the current season’s growth may 
suffer serious injury from attacks of the fungus. ‘Twenty Ounce 
apple trees are apparently the exception, since in some localities 
the trunks of this variety are badly injured. The fungus extends 
down from diseased branches or from canker spots at the forks of 
the tree till in aggravated cases large areas of bark are destroyed 
exposing the wood in ugly wounds. These patches of black, de- 
caying wood are conspicuous from a distance. Old age and neg- 
lect, or a lack of vigor from any cause evidently favor the disease 
though apparently thrifty trees are frequently ruined by its attack. 
The effect of a canker on a limb depends on the amount of bark 
that is injured or destroyed. In severe cases the disease may 
extend entirely around a limb, thus effectually girdling it. Thus 
it occasionally happens that the leaves on some part of a tree 
shrivel and die without apparent cause, but a close examination 
shows the presence of rough, dead bark somewhere on the limb, 
indicating the presence of the canker fungus which has extended 
around the limb and cut off the flow of sap. 
Plates XXVIII and X XIX are reproduced from photographs of 
typical cankered limbs. In Fig. 1 of Plate XX VIII the character- 
istic rough bark is shown and at a the wood is exposed, the white 
fruiting bodies of the fungus, Schizophyllum commune Fr., being 
conspicuous on the dead bark. At 6 is a canker spot of compara- 
tively recent formation. Fig. 2 shows the same limb from which 
the dead bark has been removed; only a narrow strip of live bark 
remained that kept the limb alive. Fig. 3 is an enlarged view of 
the more recent canker shown in Fig. 1 at 0. This canker is 
evidently of three seasons’ growth as is indicated by the three 
series of concentric lines, now rather indistinct, that at one time 
separated the dead from the living bark. The extent of the cur- 
rent season’s growth can be readily distinguished by the smoother 
appearance, while a distinct line separates the dead from the living 
bark. 
