442 BOTANICAL GAZETTE [JUNE 
Both of the latter showed steady increase in leaf dissection, 
although through an accident to the print of SA its dissection 
data could not be worked out. As with leaf area, therefore, total 
and mean duct capacity are plainly influenced by some factor 
other than senescence, doubtless environmental. 
Essentially the same statement may be made with respect to 
the ratio. (duct ‘capacity / leaf area) and to BENEDICT’s (z) cri- 
terion (vein islets / unit leaf area), from which we may at least 
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Fic. 7.—Showing, from left to right, effect of senescence on successive leaves of 
rosette; coordinates run through homologous points in each case. 
with safety conclude that the criterion for senescence in Vitis cer- 
tainly is no criterion in T. vulgare. Since the completion of the 
present work, Ensicn (6) has shown a similar lack of correlation 
between vein islet area and age in several genera, including even 
Vitis. 
Distortion figures for senescent change (fig. 7) are chiefly of 
value in showing that the successive sets of forms in a rosette can 
be homologized. They likewise show, what seems clear from 
inspection of ordinary leaves, that the increase in degree of dis- 
section is the result of an increasing degree of inhibition of the tip 
