488 RUMBOLD— PATHOLOGICAL ANATOMY OF 



chemicals. They exhibit more and more abnormahty as wound 

 tissue, until the sections show not wound tissue but stimulated growth 

 of cells. 



Fig. 3 shows a wound tissue formation in a ten-year-old tree 

 which had been injected in June and July with nitro phenol-para 

 1-500 G.M. and felled in November. The path of the main stream 

 is shown on the right-hand side of the photograph. The cells had 

 been killed and a callus had formed which was not as well developed 

 as the callus shown in Fig. 2. On the right-hand side the dark 

 streak in the xylem shows the path of the solution. In this region 

 the solution must have been much diluted as compared with the 

 main stream. Here the phloem, cambium layer (c) and year ring 

 of wood are normal, with the exception of the xylem cells in the 

 immediate neighborhood of the path of the solution. Somewhat 

 left of the center a stimulating effect is seen in an abnormally placed 

 group of xylem cells in the midst of the phloem. 



Questionable wound tissue is seen in Figs. 4 and 6. The xylem 

 formation can be regarded as irregularly formed year rings of wood. 

 In this case the growth of the rings of wood has been stimulated, 

 for the normal ring of xylem had nearly completed its growth before 

 injection began. Or the extra growth of xylem cells on the far 

 side, as regards the cambium region, of the bast-fiber groups can be 

 regarded as a form of wound tissue (callus). The premature bark, 

 which always appears with the abnormal xylem, can be regarded as 

 part of a wound tissue. Fig. 8 gives a detail showing the suggestive 

 arrangement of the protective cells, stone cells, and bast-fibers, in 

 relation to this extraordinary xylem. 



Inhibitory Effect on the Growth of the Cambium. 



This was a phenomenon common to the injected trees. Fig. 4 

 shows a section which had been cut from a sixteen-year-old tree, 

 injected with lithium carbonate 1-500 G.M. in July, August, Sep- 

 tember and October and felled in November. The section shows 

 the relation between the path of the injected alkali (s), the cambium 

 layer region (c), the irregular growth of xylem cells (x) and the 

 irregular growth of bark cambium {be). Fig. 5 shows the enlarge- 



