486 RUMBOLD— PATHOLOGICAL ANATOMY OF 



solution passed acted like a blotter, with the result that the farther 

 from the point of injection, the more dilute was the solution and the 

 smaller the injected stream. Correlated with this, the tree tissues 

 appeared more normal as the distance from a point of injection in- 

 creased and the area of disturbance decreased. Occasionally all 

 stages of reaction to an injection could be seen in a tree: death — at 

 the point of injection — retarded growth, stimulated growth and no 

 reaction. 



The results of the injections, to which particular attention is 

 called here, are of interest from a histological standpoint. 



1. A strong inhibitory effect on the growth of the cambium layer 

 was noticed; so strong that as a tissue it often disappeared. The 

 cambium cells changed into xylem. 



2. There was an irregular formation of the new year ring of 

 wood. During its formation isolated groups of xylem cells ap- 

 peared in the midst of the phloem. 



3. Phloem cells were converted into xylem by cell division fol- 

 lowed by lignification, or the cell walls were lignified without cell 

 division. 



4. All of the cells of the phloem region were capable of change 

 with the exception of the stone cells, the bast-fibers and their ac- 

 companying cells containing crystals. 



5. There was a production of wound tissue showing various 

 degrees of abnormality. The wound tissue was abnormal in that 

 its position was reversed from the one in which it is customarily 

 seen, and frequently the cells composing it had unusual shapes. 



6. Cork formed prematurely. It was apparently correlated with 

 the irregular growth of xylem in the phloem region. 



Another region of response to the injections was the xylem, 

 evidenced by an increased formation of thylloses and a thickening 

 of cell walls. This response, while pathological, was one which was 

 expected. For this reason no emphasis is placed upon it in this 

 discussion, but it will be referred to in connection with the paths of 

 the injected solutions. 



These points can be elucidated best by a view of some sections 

 cut from injected trees. They have been selected from many, as 

 they illustrated the points emphasized in this paper. 



