WOUNDING OF FOUAGE EEA¥ES 
295 
Cutting major lateral veins, with or without destruction of mid- 
rib. (3) Injuries to blade between the principal veins. (4) 
U-sbaped cuts leaving peninsulas of living tissue. (5) Parallel 
slashes ending inside the periphery of the leaf. (6) Cuts par- 
allel to the midrib extending through the outer end of the leaf. 
Fig. 49. Feaves with midribs interrupted in one or more places. 
I. Injuries to the midrib {Fig. 4p ). — The midvein occupies 
such a prominent place in the architecture of the leaf that it was 
naturally supposed to be essential to the work of this organ. 
Trials soon established, however, that any of the broader leaves 
studied could get along readily with a section of the midrib re- 
moved. Leaves with broader blades seemed to thrive even after 
the midvein had been destroyed through practically its entire 
length (b, g). 
The cleft leaves of oak presented difficulties for if the midrib 
were interrupted opposite the narrower part of the blade only 
a slender lateral margin was left for conduction and support. 
If the leaf suffered too great water loss a part of the distal area 
died (c). A smaller oak leaf (e), growing in a somewhat pro- 
tected position, survived the loss of midvein without death of 
remaining tissue. Wounds in the broader portions of these leaves 
offered no difficulty even when lateral veins were cut (d). 
In all these cases the life of considerable portions of leaf- 
tissue was conditioned upon conduction, for a minimum distance 
