282 TAYLOR— ON THE PRODUCTION OF 



reported by Dr. Rumbold, their behavior during the second year of 

 growth, and the condition of the tissues prerequisite for their formation. 



As a result of an extensive wound, the growth of the normal wood 

 cambium is stopped for a short distance above and below the wound. 

 In the region thus affected, there may form in the soft-bast of the bark 

 two principal types of lignified tissue not normally present there. 



The simplest type consists of lignified soft-bast cells, the other is a 

 xylem resulting from the assumption by soft-bast cells of a meristematic 

 character. 



In the latter case the first cells to become active are those on the 

 outer faces of the hard-bast strands, and the cells external to these 

 become involved successively. 



These meristematic cells divide, and the products become matured 

 into the elements of a xylem which closely simulates normally formed 

 xylem. 



A considerable part of the tissue between two or several rings of 

 hard-bast strands may be re-formed in this manner over a considerable 

 area, the patches of soft bast-cells that remain either being unaltered in 

 structure, or the walls become lignified without marked change in the 

 shape of the cells. 



The cells between the adjacent strands of hard-bast of the same ring 

 come to take part in the changes, and in such regions the cells become 

 much distorted, and may appear intermediate in form between lignified 

 bast cells and xylem elements. 



The medullary rays in the region of the formation of the xylem patches 

 grow with them and form rays similar to those in the normal xylem. 



Eventually a fairly normal cambial region forming phloem as well 

 as xylem is developed from the outermost of these meristematic areas, 

 and, so far as the material indicated, further growth proceeded from 

 this in much the usual fashion. 



The Injection of Herbaceous Plants 



Material and Methods 

 As has been stated, this part of the work was instituted to obtain 

 evidence explanatory of the conditions found in Castanea. Naturally the 

 first method attempted was that used by Dr. Rumbold on Castanea (2). 

 The softness of the stem in the actively growing regions rendered difficult 

 the obtaining of a water-tight connection between the stem and the 



