2 9° Mr. T. A. Knight on the action of 
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 sur- 
rounded by two folds of paper coated with wax on each side ; 
by which all connection 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 organizable 
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 circum- 
ference, and being found to consist of matter apparently 
