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IOWA ACADEMY OF SCIENCE Vox.. XXVIII, 1921 
sustained by an isthmus only a little over one millimeter wide 
and without any prominent vein. 
V. Cuts ending within the periphery of the leaf. — A. Trans- 
verse cuts, Fig. 53. In general leaves may be cut across the cen- 
tral portion of the blade, severing the midrib and basal major 
veins, without death of tissue. Even the most sensitive leaves 
like Vitis and Basswood (f) withstood successfully single trans- 
verse cuts through the central two-thirds of their width and in- 
terrupting all the primary venation. In Eilac (c, d), Symphor- 
iocarpos (a), and Elm a series of parallel transverse cuts, sep- 
arated by less than one centimeter of leaf tissue, and extending 
two-thirds of the distance across the blade, produced no appar- 
ent disturbance of the functions of the leaf. In Basswood (g) 
such wounding resulted in the death of a fan-shaped area of the 
blade broadest at the apex of the leaf and narrowing to a point 
beginning above the lowest transverse cut. As discussed below 
the difficulty with Basswood seems to be associated with its ar- 
rangement of secondary venation. In Oak (e) single cuts, pene- 
trating into the opposite lobes and extending over one-half of the 
distance across the leaf, left the distal portion of the leaf appar- 
ently uninjured. The shape of these oak leaves did not permit a 
series of parallel transverse cuts. 
The path of conduction, in a leaf with parallel transverse cuts, 
is not only greatly lengthened but is complicated by the presence 
of larger veins, lying across the trend of conduction. A little 
consideration will show the extremely difficult situations en- 
countered by Symphoriocarpos (a) or Lilac (c, d). 
B. Longitudinal sections or cuts. Leaves are in general less 
tolerant of . slashes parallel to the midrib than to those at right 
angles to its axis, this due in part to the fact that cuts in this di- 
rection cross the major veins at a sharp angle thus leaving bar- 
riers to the movement of water along the strips. This series 
confirms findings of above noted experiments as to relative ^'sen- 
sitiveness” of different leaves. There were brought out strongly 
also the effects of cross veins as barriers, and the importance of 
adequate supply to base of any given strip of blade. If the 
slashes begin higher in the leaf, somewhat above the base, the 
results are much more successful. In these experiments Asclepias 
was the least able to endure wounding, with Basswood second. It 
was noted that in both of these there is a marked increase in the 
efficiency of the conduction in the marginal region. 
VI. Cuts parallel to the midrib and extending through mar- 
