74 LEAF-CLIMBERS. Cuap. II. 
can hardly be removed from its support. On com- 
paring a thin transverse slice pf such a petiole with one 
from an older leaf growing close beneath, which had not 
clasped anything, its diameter was found to be fully 
doubled, and its structure greatly changed. In two 
other petioles similarly compared, and here represented, 
the increase in diameter was not quite so great. In 
the section of the petiole in its ordinary state (A), 
we see a semilunar band of cellular tissue (not 
Fig. 4. 
Solanum jasminoides. 
A. Section ofa petiole in its ordinary state. 
B. Section of a petiole some weeks after it had clasped a stick, as shown in fig 3. 
well shown in the woodcut) differing slightly in 
appearance from that outside it, and including three 
closely approximate groups of dark vessels. Near 
the upper surface of the petiole, beneath two exterior 
ridges, there are two other small circular groups of 
vessels. In the section of the petiole (B) which had 
clasped during several weeks a stick, the two exterior 
ridges have become much less prominent, and the two 
groups of woody vessels beneath them much increased 
in diameter. The semilunar band has been converted 
into a complete ring of very hard, white, woody 
