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into scattered yellow globules. Beneath the outermost cell layer, which at 

 once collapses and forms a protective mantle for the underlying young 

 tissue, the new cell formation begins by means of cross walls. The 

 medullary ray, the cells of which as a rule are in advance of the others, is 

 frequently broadened by this new formation since the later ray cells push 

 out in a fan over the adjoining wood cells. 



It has already been stated that often the medullary ray cells can remain 

 partially or entirely undeveloped. Then the parenchymatous callus cells, 

 which are never round but always polygonal, and are produced from the 

 young wood fibres, spread over the medullary ray groups. As a rule, how- 

 ever, the whole tissue participates equally in the formation of a thin callus 

 layer which pushes out the outermost cells of the old wood. By drying 

 these old cells produce a protecting layer. 



While the callus formation through the excrescent apical growth of 

 the various cell rows is very considerable in the barked places, which are 

 kept protected and moist, it is very small in unprotected places. Cork is 

 formed at once beneath the dried, outer cell layer and becomes a constrict- 

 ing, firmly protecting girdle for the underlying young tissue, which is 

 turning green. 



The new formation of bark on barked places may occur in still another 

 way. If the bark wound is made in such a way that young bark cells form 

 the outermost layers of the exposed surface, they initiate the callus forma- 

 tion and the real cambial layer is only slightly disturbed. 



The transition of the callus into normal tissue takes places in general 

 in such a way that isolated, short celled, vascular strands occur deeper 

 inside the callus after the cork cells have begun to form about its edge. 

 About this time thick-walled, slightly porous, irregular, or polygonal cells 

 are found, possibly in the same radial direction but more in the vicinity of 

 the peripheral zone of the callus. These cells are the first traces of a phloem 

 formation. In many trees, the first phloem elements in the form of aggre- 

 gations of stone cells are found isolated or soon united into groups. In one 

 zone, cells with a cloudier, denser content are found between the phloem 

 and the vessel elements. In them occur a great many rectangular walled 

 cells, somewhat stretched in the direction of thd long axis of the trunk, 

 which might be the very first stages of the newly forming camhimn. From 

 this cambium are produced gradually the elongated elements which finally 

 develop into normal wood and fibres but no more long, spiral elements seem 

 to be formed. 



With the development of these normal fibres, the last to appear, the 

 new bark may take on the function of the uninjured bark. 



The Bending of the Branches. 



Branches are often bent as a special aid in fruit culture. Experience 

 shows that shoots which grow upright develop most quickly and strongly 

 and that their growth in length will be the more retarded, the further the 



