792 



The cambial zone, which runs close to the prosenchymatous wood 

 elements in that part of the normally developed vine which lies below the 

 place of the cut, describes a wide circle c,c,c' at its entrance into the wound, 

 or overgrowth wall ; it divides the apparently uniform ground tissue into one 

 part lying against the old wood body of parenchyma cells with strong, porous 

 walls, the ivound wood (zvh), and an outer part, the wound bark (wr). In 

 the clearly marked, radiating arrangement of the individual cell rows, this 

 row is recognized as a secondary growth of the cambial zone, appearing 

 very early in the callus roll. The elements formed from the cambial zone 

 have approximately the same parenchymatous form in the same horizontal 

 surface, only, as already said, the parenchymatous wood (wh) differs from 

 the bark tissue by its porous walls, which are more greatly thickened and 

 more dense and, therefore, lie against one another with sharper angles; a 

 stronger pressure has already made itself felt here. 



But an evident differentiation is noticeable in the bark tissue itself. 

 Between the somewhat oval cells, forming the ground mass of the bark, we 

 find more elongated, more slender, somewhat prismatic cells arranged in a 

 curve (b") approximately parallel to the cambial zones. These represent 

 the very beginnings of the hard bast cells. They are richer in content and 

 accompanied by pouch-like cells, which, in their longer axis, usually run 

 parallel to the young bast bundles and contain raphides of calcium oxalate 

 (o). The bark tissue produced from the youngest bark already formed at 

 the time of cutting and containing thick-walled, but short and broad hard 

 bast contains its calcium oxalate in the form of stellate druses, or separate 

 crystals, similar to those which occur chiefly in the normal bark (o'). At the 

 place of the transition, raphides and stellate druses are often separated from 

 each other only by two cells. Here also only the loosely constructed tissue 

 contains raphides. 



The parallel arrangement of the crystal-containing cells, with the bast 

 fibers, is seen best in tangential section in the cherry ; here the base bundles, 

 lying in a net work upon one another, are found to be accompanied by 

 parenchymatous cells lying close against one another and elongated. Almost 

 every one of these contains a crystal of calcium oxalate. In the grape this 

 is less sharply marked and becomes relatively indistinct as the tissue, as a 

 whole, loses its differentiation in the overgrowth walls. In this less differ- 

 entiated part may already be recognized thicker walled elements lacking the 

 deposition of calcium oxalate in the surrounding tissues. The calcium 

 appears in the cells formerly filled with starch, a fact which indicates that 

 the calcium oxalate is one of the end products in the solution of the carbo- 

 hydrates. 



Therefore, no calcium oxalate is found in the outermost peripheral 

 zones of the overgrowth edge because these zones consist of the first formed 

 tissue of the quickly growing undifferentiated callus projecting beyond the 

 cut surface. In these the material has been utilized entirely for cell increase 

 and is not deposited in the end as reserve starch. On the whole, however, 



