Fig. 53. L.eaves with one to several slashes across the blade. 
leader though one or more of the larger veins ran parallel with 
the longer dimension of the peninsula (h). In some the veins 
did not aid but were barriers because they ran across the area at 
various angles thus interrupting the inward flow of water (j). 
The peninsulas in all cases except certain sun leaves (b) sur- 
vived. The failures were associated usually with barrier veins 
running across the peninsulas in such way as to cut off conduction. 
Leaves with similar or even more severe exposure, if free from 
such barriers, showed no dead tissue (i). In a number of these 
experiments conditions were accidentally made very difficult. 
For example, in one of the cuts on Elm (e) a grasshopper ate 
out a portion of the base of the upper right hand peninsula, great- 
ly reducing its width, and a tear due to wind narrowed the living 
margin outside, yet this peninsula survived. 
The significant results of this series of experiments is that the 
minor venation of a leaf is not only sufficient to care for ad- 
jacent tissue but may be forced to accommodate large areas de- 
manding a greatly increased flow. The direction of water move- 
ment may be readily reversed. In peninsulas free from barrier 
veins the area that may be sustained by a narrow isthmus of 
blade, without any assisting larger veins, is surprisingly large. 
One peninsula in Lilac (h. left) with an area of 175 sq. mm. was 
WOUNDING OF 
leaves 
