334 
Journal of Agricultural Research 
Vol. XI, No. 7 
The explanation of this phenomenon is, no doubt, that the inhibited 
photosynthetic and respiratory activities, together with the increased 
permeability of the cell walls, occasion the closing of the stomata. This 
reduces stomatal transpiration more or less completely. Cuticular 
transpiration, however, can continue as usual; in fact, with the increased 
permeability of the leaf septa, it might even be augmented. In order to 
demonstrate the hypothesis, two groups of tomato plants were kept in 
Fig. io.—T ranspiration curves of tomatoes as affected by hydrocyanic-acid fumigation. Arranged from 
top to bottom in order of increasing injury. 
absolute darkness before, during, and after fumigation. The loss in 
water under these conditions represents loss through the cuticle of the 
leaves, since the stomata are closed. The curves in figure 11 show that 
there is a considerable increase in this phase of transpiration in the 
fumigated plants. Meanwhile the increased permeability has resulted 
in decreased osmotic pressure in the tissues, which would slacken, or stop 
altogether, the inflow of water from the stems. Consequently the water 
