AREA OF VEIN-ISLETS IN LEAVES OF CERTAIN 
PLANTS AS AN AGE DETERMINANT 
M. R. Ensign 
(Received for publication February 26, 192 1) 
The available evidence in support of a theory of senescence in plants 
is very meager. The work of Minot (7), Child (2), Hertwig (5), Conklin 
(3) and others establishes quite definitely that complex animal forms are 
subject to a gradual retardation of physiological functions; also, that this 
retardation begins in the embryo and continues with more or less acceler- 
ation until death ensues. 
Benedict (i) has attempted to show that plants are subject to similar 
changes of physiological functions. These, he claims, are initiated im- 
mediately after fertilization and are registered in the increasing complexity 
of the vascular ramifications in the leaves of certain dicotyledonous plants. 
In other words, the relative age of such perennial plants as vines, trees, 
and shrubs can be detected by determining the relative area of the "tissue 
islands" or vein-islets formed by the intersecting veins surrounding them. 
Old or senile plants, therefore, produce leaves whose vein-islets are smaller 
in area than those in leaves of young plants of the same species grown under 
similar environmental conditions. 
Beginning with these premises, the writer (4) studied the venation of 
leaves produced by polyembryonic Citrus seedlings {Citrus grandis). 
During the progress of this work certain questions arose regarding the 
accuracy of the methods employed by Benedict in determining the area of 
vein-islets in the leaves which he used. In order to shed some light upon 
this point the work herein reported was undertaken. The data collected 
are not as extensive as might be desired, but inasmuch as further investi- 
gation had to be postponed indefinitely, they are presented for what they 
may be worth. 
Methods and Materials 
Leaves from the following plants were studied with reference to their 
venation: Berheris vulgaris L., Berberis Thunbergii DC, Castanea dentata 
Borkh., Quercus alba L., Fagus caroliniana Fernald and Rehder, Vitis 
vulpina L., and an undetermined species of Vitis growing in the physiological 
greenhouse at Cornell University, Ithaca, New York. The trees and vines 
grew in the immediate vicinity of Ithaca, and the barberries grew on the 
university campus. 
In collecting the leaves from these plants the trunk diameters were 
taken as an index of relative age. For comparison two or more plants 
433 
