278 TA\TOR— ON THE PRODUCTION OF 



soft-bast between one hard-bast strand and the next outer become 

 completely re-formed to xylem. There seemed always to be the inter- 

 vening zone of lignified (or unHgnified) non-xylem elements. In large 

 and well-developed xylem-patches the distribution of elements resembles 

 that in the year-ring of wood, the majority of the pitted vessels being 

 inside, with the fibers on the outer face (Plate LXXIV, Fig. 12). 



The elements of the xylem formed in this peculiar manner resemble 

 those of the normal xylem very closely, differing from them in certain 

 minor points only. They are somewhat smaller in size, and show the 

 peculiar pit markings more prominently (Plate LXXIII, Fig. 8). Fre- 

 quently they are twisted and deformed, and occasionally the pitted 

 vessels are completely bent over at right angles to the normal. The 

 pitted vessels also show the manner of their formation from several 

 cells fused together end to end. These peculiarities are seen along 

 the junction of two modified patches, where the wood forming normally 

 around to one side of the transforming region meets and joins with that 

 formed from the temporary xylem-cambia, and also in the first xylem 

 formed from the new bundle cambium in the manner described below. 



Before touching upon this, it is necessary that the matter of simple 

 lignification be considered. This phase was very generally present. 

 The cells on the inner side of the hard-bast strands were those that 

 acted in this manner most constantly. Here the space between one 

 hard-bast strand and the xylem area already formed on the outer face 

 of the next inner hard-bast strand is often entirely filled by these lignified 

 soft-bast cells. Lignification does not proceed rapidly, and may be 

 completed in the deeper parts of the abnormal area only. Frequently 

 there is to be seen a mixture of Hgnified and of unlignified elements 

 (Plate LXXII, Fig. 6). The lignified cells are prominently pitted. Al- 

 tho the tannin-filled cells do not take any initiatory part in the transfor- 

 mation, they as a class become more completely hgnified than the ordinary 

 soft-bast cells. The circumferential lines of these cells, lignified, may 

 cross considerable areas of unchanged soft-bast. What has been said 

 of these applies equally to the medullary rays of the bark, which also 

 contain much tannin. 



The soft-bast cells in the region of simple lignification show but 

 little tendency to change their form. They appear considerably larger 

 than the unchanged cells, but this is in part due to the shrinkage of 

 embedding, which affects only the soft, unchanged cells. 



In one place where the soft bast lignifies there does appear a change 

 of form. The outward growth of the individual abnormal xylem areas 



