Curvature of Tendrils. 397 
Action of the parenchymatous cells in plasmolysis, curvature , 
and coiling. During the course of my work on the morphology 
and anatomy of the tendrils of Passiflora coerulea I had 
occasion to examine many hundreds of cross and longitudinal 
sections of the irritable portions which had been killed by 
immersion in acetic alcohol. The changes in the stature of 
the cells of the concave side were marked and significant, and 
seem to offer a complete solution of the problem. When 
active tendrils are placed in the acetic alcohol solution, they 
execute a number of rapid oscillating curvatures and are 
shortly fixed by the action of the reagent. In such tendrils 
the parenchymatous cells had all been slightly plasmolysed 
before fixation. The outer two or three layers of the cells 
of the concave side had been moreover diminished in length 
from 20 to 40 per cent in size, and taken on a globoid form 
quite similar to that attained in simple plasmolysis. By 
reason of such change of volume and shape, the surfaces of 
contact with the neighbouring cells had been greatly 
diminished. The contraction of the protoplast around the 
central vacuole had almost obliterated it. At the same time 
numerous aggregation-bodies had been formed. On the 
convex side of the organ, the more attenuated protoplasts 
were not so much affected, and only modifications of minor 
importance had occurred, and the aggregation-bodies were 
noticeably absent. It seems entirely warrantable to connect 
the structure and behaviour of the cells of the concave side 
with the curvature of the tendril, especially since these 
features correspond almost exactly to certain characteristics 
of other known contractile cells. The action of the stimulus 
upon the cells of the motor zone, which are highly turgid, 
doubtless results in an increase of the permeability of the 
protoplasm and the consequent escape of water into the 
intercellular spaces. The outward passage of the fluid is 
facilitated by the highly-porous condition of the walls. This 
loss of water allows the elastic contraction of the highly- 
stretched walls of the cells affected, and also of an amount of 
contraction of the collenchymatous epidermal and vascular 
