Reciprocal Influence of Scion and Stock. 281 



Figure 4 presents in a diagrammatic way the natural re- 

 lationships of the several associations, the arrows indicating 

 the physiographic successions. Geographically, all of the asso- 

 ciations and formations belong to the Northeastern Conifer 

 Forest center, and taken as a whole exhibit a rather typical 

 composition. 



THE RECIPROCAL INFLUENCE OF SCION AND STOCK. 

 By W. B. McCallum. 



In spite of the voluminous literature upon the question of 

 the icciprocal influence of scion and stock the problem still seems 

 to be one of controversy. Recent physiological literature, how- 

 ever, contains a number of contributions which add very mater- 

 ially to our information on the subject and may enable us to get 

 a somewhat cleaier idea of the phenomena involved. The 

 problem is of more than horticultural interest, for it offers to the 

 physiologist instructive material in the study of correlating in-* 

 fluences between members of the plant body. When a part of 

 the plant, for example a shoot or bud, is taken from its normal 

 position and placed in a new, and perhaps quite different, re- 

 lation to the rest of the plant, both morphologically and physio- 

 logically, its behavior gives us some clue as to the formative and 

 other influences exerted upon it by the adjoining parts. 



A certain confusion of interpietation exists on account of 

 thi criteria often taken to denote change in the scion or stock. 

 Natuially the changes most looked for are such as appear in 

 differences in size, foim, color, etc. of foliage, or fruit, or other 

 parts, changes in the rate of growth, and like phenomena. It 

 is, of course, apparent that profound physiological changes may 

 have occurred without having been manifested in any of these 

 ways. Indeed, as shall be mentioned later, some of the most 

 important results of grafting are of this order. Some investiga- 



