296 IOWA ACADEMY OF SCIENCE Vou XXVIII, 1921 
at least, through minor veins which were also compelled to as- 
sume increased responsibility in the mechanical support of the 
blade. 
11. Cutting and major lateral veins (Pig. 50). — With the ex- 
ception of the more exposed Basswood leaves (d, e), all these 
Fig. 50. Feaves with one or more interruptions of major lateral veins. 
under study tolerated two or more interruptions of each major 
lateral vein. In some of the broader leaves the midrib was also 
interrupted, thus disturbing the entire major venation without 
seeming injury to the blade. An oak leaf (Fig. 49, d) with all 
large veins interrupted in the wider part of the blade near middle 
of leaf suffered no death of tissue. 
The results here confirm those of the above noted experiments 
indicating great capacity on the part of the islet borders for con- 
duction. They seem able not only to carry abnormal loads but 
show their adaptability in that conduction may be carried on in 
changed direction. 
III. Injuries to blade between the major veins {Pig. 51 ).-— 
Foliage leaves are most commonly injured, whether by leaf eat- 
ing insects or other agency, in. the areas between larger veins. As 
