39 2 Mac Dong cd. — The Mechanism of 
active cells. After a tendril has reached the end of the grand 
period of growth, the formation of free coils in either an 
attached or unattached tendril of Cuciwbita occupies from ten 
to eighty hours, and is modified only by the traction exerted 
by the weight of the stem which it supports. The manner in 
which strains may arise or be induced, and their continuance, 
point to the conclusion that curvature in response to contact- 
irritation and the formation of free coils are entirely distinct 
physiological processes 
Anatomy and Morphology. 
The most important facts in the localization and determina- 
tion of the action of the motor zones would be those obtained 
by a consideration of the anatomy and morphology of the 
tendril with especial reference to the structure and arrange- 
ment of the parenchymatous tissue lying between the vascular 
and epidermal systems. Curiously enough an examination of 
the changes in structure and stature of these cells for the 
foregoing purpose has not heretofore been made. 
Although the work in hand has been extended to cover 
a large number of species of Cucurbitaceae and Passifloreae, it 
will be most convenient to restrict the discussion to the 
above-named features of Passiflora coerulea , P. mcarnata, and 
P. Pfordti , which the author has had under more or less 
constant observation for several years. The tendrils of these 
species are tapering filamentous organs of ovoid cross-section, 
attaining a length of 20 to 30 cm., and a diameter at base of 
2 mm. decreasing at the tip to 1 mm., which for a length 
of -5 cm. is curved into a characteristic hook-form. The 
tendril makes its appearance as a lateral conical projection 
from the growing point, in the axil of a leaf (XXII), and 
shortly by reason of the accelerated growth of the periblem, 
there is formed, on the summit of the cone, a cup-shaped 
depression, which becomes more and more marked, and by 
reason of the excessive growth of the convex (upper) side of 
the tendril it faces laterally (or downward) when the tendril 
