ON THE ACTION OF DETACHED LEAVES OF PLANTS. 



169 



A slender knife was passed through some leaf-stalks of the vine, about 

 two-thirds of an inch distant from their junction to the branch ; and, 

 down to that point, the leafstalks were divided longitudinally, and a 

 transverse section, about half-an-inch long, was made through the bark 

 opposite the middle of the leaf-stalk. A similar transverse section 

 through the bark was made somewhat less than an inch distant below ; 

 and these sections were united by two longitudinal sections through the 

 bark, which extended from the extremities of the upper transverse 

 sections to the extremities of the lower ; by which means pieces of bark, 

 about half-an-inch broad and nearly an inch long, were separated from 

 the adjoining bark. These were then detached from the alburnum, and 

 surrounded by two folds of paper coated with wax on each side ; by 

 which all connexion and communication with the tree, except through 

 the divided leaf-stalks, were cut off. The insulated pieces of bark, 

 nevertheless, continued to grow, and extended downwards, and laterally, 

 and in thickness ; and thin layers of alburnum were deposited. 



Leaves of the potatoe, without any portion of bark being attached to 

 them, were taken from the plants just at the period when the tuberous 

 roots began to be formed ; and I conceived that these leaves, consistently 

 with my former experiments and conclusions, must contain portions of 

 the living organisable matter which would subsequently have been found 

 in their tuberous roots. The leaves were therefore planted in pots, and 

 placed under glass, where, being regularly and properly supplied with 

 water, they continued to live till winter, though without emitting fibrous 

 roots ; and I then expected to find some small tubers at their bases. In 

 this expectation I was disappointed ; but the result of the experiment was 

 not less satisfactory, the bases of the leaf-stalks themselves having swollen 

 into conic bodies of more than two inches in circumference, and being 

 found to consist of matter apparently similar to that which composes the 

 tuberous roots of the plant. The enlarged parts of the leaf-stalks 

 remained alive in the following spring ; but whether they are capable of 

 generating buds or not I have not been able to ascertain. 



Leaves of mint were planted in the same manner as those above- 

 mentioned; which grew, and continued alive through the winter, and 

 were still living in the end of the last month, having assumed the character 

 of the thick fleshy leaves of evergreen trees. Upon examining the mould 

 in the pots, 1 found it to contain very numerous roots, which must have 

 derived their medullary, and their cortical, and alburnous substances, 

 from matter which had emanated and descended from the leaves. 



I had frequently observed, in former experiments, that the destruction 



