Cuar, IL. SOLANUM. q3 
weighing only ‘82 of a grain (53:14 mg.) We have 
seen that the petioles of some other leaf-climbing plants 
are affected by one-thirteenth of this latter weight. In 
this species, and in no other leaf-climber seen by me, 
a full-grown leaf is capable of clasping a stick; but in 
the greenhouse the movement was so extraordinarily 
Fig. 3. 
Solanum jasminoides, with one of its petioles clasping a stick. 
slow that the act required several weeks; on each 
succeeding week it was clear that the petiole had 
become more and more curved, until at last it firmly 
clasped the stick. 
The flexible petiole of a half or a quarter grown 
leaf which has clasped an object for three or four 
days increases much in thickness, and after several 
- weeks becomes so wonderfully hard and rigid that it 
