702 



cases I have found the initial stages only in the cambium itself and, in fact, 

 more frequently in the peach than in the cherry. 



However, where the initial stages can be found, the evil is always 

 dangerous because it spreads further. Gummosis produced in the wood soon 

 spreads to the cambium and the bark, when it becomes very extensive in the 

 bark, and thus may furnish the greatest part of the gum on the exterior of 

 th6 trunk; the cambium also does not escape later. The assertion that 

 gummosis always begins in the cambium is correct only if by cambium is 

 meant the primordia of imperfectly developed cells which later fall victim 

 to liquefication. The profess of liquefication itself can begin at any place in 

 the branch and long after the formation of these tissues has taken place. 

 On this account, we find gum holes in the middle of the wood body. 



The ultimate result is essentially the same. At some point in the cir- 

 cumference of the trunk, the cambium is finally destroyed and the already 

 matured wood becomes more or less diseased. A wound thus appears 

 which spreads further and further. This, however, is not always recog- 

 nizable externally, for the diseased place is not indicated by gum which has 

 exuded to the outside. The gum comes to the surface rarely, or only very 

 late, if the cambium is first attacked by gummosis. Then the solid, already 

 matured wood dies slowly and, in fact, gradually more toward the centre of 

 the trunk, i. e. toward the pith (Fig. 155 2k) than toward the circumfer- 

 ence. This arises from efforts at localization, which occur simultaneously 

 with the disease. A case illustrated in the drawing (Fig. 155 i g) and 

 occurring not infrequently, consists in the drying up of the bark above the 

 affected wood, with the exception of a few bast bundles, and not its dissolu- 

 tion. At that place, the part marked IV in the figure is bridged over by 

 bark elements (Fig. 2 r). The formation of gum is not very extensive but 

 the attempt of the tree to heal the wound becomes more noticeable. This is 

 perceptible in one-year-old branches. Figure 155 i, illustrating a gnm 

 pocket a year old, shows at u the attempt of the tree to overgrow the place 

 (during several years) : a indicates a branch. 



A more abundant formation of wood and bark on the healthy part of 

 the trunk, lying next to the wound (Fig. 155 2 h) makes the trunk thicker 

 on the wounded side than on the healthy side (!') and above and below the 

 wound. If the bark is retained above the wound the edges of the over- 

 growth (Fig. 155 w) have raised the dry bark from the dead wood and in 

 this way a cavity forms of which the back wall is formed from the wood 

 and pith partially attacked by gummosis and the front wall by the dry bark 

 (not drawn in the figure) and the sides of the freshly formed callus (« u). 

 The cavity thus produced is a lodging place for insects and fungi. 



The newly formed callus, however, rarely remains intact. In the 

 majority of cases, small gum centres (Fig. 155 2d') are found in the lux- 

 uriantly developed new tissues. To be sure, the living bark attempts to 

 enclose the diseased places by layers of cork, but I have never been able to 



