338 Harris M. Benedict 



It is not possible at present to state the precise nature of the change in 

 meristematic cells which forces the production of more vascular tissue at 

 the expense of parenchymatous tissue. Later in this paper an attempt 

 at an explanation will be made. 



IMBIBITION OF WATER BY POWDERED LEAVES OF YOUNG AND OF 



OLD VINES 



The amount of water imbibed by the powdered tissues of leaves gives 

 an indication only of the relative water-holding capacity of the hving 

 leaves. Is there any difference in the behavior of leaves from young and 

 from old vines toward water of imbibition? 



A large number of leaves were collected from various vines of Vitis 

 vulpina with from six to eight rings and from twenty to twenty-five rings. 

 These leaves were ground fine in a meat grinder. Each ground mass was 

 immersed in acetone for ten minutes, filtered under suction, and dried in 

 a crucible for three days at a temperature of 90° C. The dried masses 

 were then thoroughly pulverized in a mortar to the same degree of fineness, 

 the heavier veins and the more numerous veinlets of the older material 

 requiring more grinding than the younger. There were thus obtained 

 about 100 grams of leaf powder from the younger vines and the same 

 quantity from the older ones. The individual vines were not kept sepa- 

 rate but all those of similar age were mixed together. 



DEGREE OF IMBIBITION WITH DISTILLED WATER 



In order to determine the degree of imbibition of water by powdered 

 leaves from young and from old vines the procedure adopted was as 

 follows: In three graduated glass tubes was placed 0.5 gram of the 

 powder from leaves of young vines, and into three other tubes the same 

 quantity of powder from leaves of old vines. Distilled water was added 

 to each. The material from young vines increased in bulk from a height 

 of 30 milhmeters to one of 50 millimeters, while that from old vines 

 increased only from 25 to 38 milhmeters; the percentage increase of the 

 leaves from the young vines being 66, and that of the leaves from the 

 old vines being only 52. 



This result proved to be a constant one, there being minor variations 

 in the percentages, but the powder from the young leaves always averaging 

 about 14 per cent greater absorption. This difference might be due to a 



