820 



edge to the normal wood structure, as it gradually forms in the later annual 

 layers above the place where the wire is. 



If the wood had grown normally, without the arrestment of the wire, 

 its structure would have necessarily remained the same as before it was 

 constricted, as represented at //; wood cells (h) with vessels (g) would 

 have been formed in regular succession and this broad wood would have 

 been uniformly divided by radially extending medullary rays (w). Instead 

 of this, we find the constricted place and above it (h',h) a kind of wood 

 produced by the effect of the wire composed almost entirely of wood cells 

 without vessels. Only in the beginning are these wood fibres deposited at h' 

 exactly parallel with the long axis of the branch; the more they are found 

 in tlie direction {h',h" ') the more diagonally they run and the more twisted 

 they seem. The wood formed after the wire has been bound on has, there- 

 fore, become denser, poorer in vessels and more twisted. The medullary 

 rays, which otherwise run as straight radial bands from the pith toward the 

 I ilk. are as twisted and outspread toward the top as the wood cells, so that a 

 section made exactly in the direction of the radius intersects several of the 

 curved rays (w"). 



The difference between the wood cells and medullary ray cells is not 

 noticed until at some distance from the wire. In the immediate vicinity of 

 this we find an almost uniform parenchymatous wood (hp), of which the 

 edge is dead and black and represents the dark line which may be seen in 

 Fig. 196, s, extending upward a little distance from the wire {d'). The 

 t)lack furrow no longer extends entirely to the outside, since the later 

 annual layers (Fig, 196, 5,w') have already united with one another. These 

 overgrowth edges, united with one another to form a common, connected 

 wood layer, are indicated in Fig. 196, 4, by the tissue H.' Here we find the 

 ducts (g) and the wood cells {nh') formed as in normal wood (only 

 shorter) but their course is horizontal instead of vertical in the plane lying 

 at the same height as the wire. Only at some distance from the actual place 

 of constriction upward or downward do these elements begin to pass over 

 gradually into their normal perpendicular course (Fig. 196, 4 g'h'). The 

 browned, or blackened, zone {hp) is not continued to U'. 



The term "browned" or "blackened" has not been chosen without good 

 reason, for the color from t to t' is as black as ink, from there toward t" a 

 brownish black. In fact, it is ink which colors the clotted cell contents near 

 the wire. The tannic acid of the tissue has combined with the iron of the 

 wire and, therefore, killed the cell contents in the immediate vicinity. 



This compound is diffused for considerable distances and, in fact, 

 farther into the old wood through the medullary ray tissue than transversely 

 through the wood cells. The fact that the wire lies directly against the old 

 wood and has killed a zone of it should not be surprising, when we think 

 that the constantly increasing pressure of the distending branch against the 

 inHexible wire, leads to the compression of the soft bark and the cambium 



