38o 



removed, the wood showed the spike-like processes of the dead bud cones. 

 The surface view is given at a; at b the cross-section of the spike-Uke wood 

 cones with the medullar}' parenchyma indicated by the darker inner circles. 

 Similar structures appear in very different tree genera and at will in 

 places on the aerial axis as well as in the buds of the root stock, — but here 

 more rarely. The places exposed by the removal of branches are especially 

 preferred. Here the latent and adventitious buds, accumulated at the base 

 of the branch, begin to develop into small shoots. The wood elements, 



Fig. 60. 

 C'ros.s-section through a g-narl cushion. 



Fig. 59. Formation of gnarls on 



the branches of Malus sinensis. 



(After Kissa.) 



It is seen that the central part of the indiviclual sj: 

 the iriiarl is produced 1)\- a broadeningr of tlu- niii 

 ra.\ of tile branch axis. (After KisSA.) 



arising from the cambium of the trunk, take a serpentine course around the 

 bud cones, because they are prevented by them from extending through the 

 cambium. The plastic food material is, therefore, not conducted so readily 

 towards the base of the trunk. But the economy of the tree suffers little, 

 as the gnarled swelling usually occurs on one side of the axis, so that the 

 opposite side lies free and remains constantly accessible for normal 

 nutrition. 



Nevertheless, normal branch primordia may not always be assumed as 

 the points of departure of gnarl formation. There are also cases in which 

 the spikes of the gnarl arise from excrescences of the medullary rays. One 



