Curvature of Tendrils. 379 
was increased, and the growth in length of the concave side 
was lessened. Thus in a length of 1 mm., the increase on the 
convex side was 1*4 mm., on the concave side *i mm., and in 
a neighbouring unstimulated portion, *2 mm. on both sides. 
These figures express the total amount of change during the 
formation of the contact-curvatures around the support, and 
the ensuing growth during a period of twelve to forty-eight 
hours. Further, both Sachs and De Vries agree that at times 
an actual contraction of the concave side occurs in many 
instances. In the tendril of the Gourd, the actual shortening 
of the concave side amounted to one-third the length of the 
tendril at time of stimulation (I, II, XX), a fact which is 
not adequately explained ; and it may be shown that the 
changes in length of the portion of a tendril which are caused 
by a contact with a support, and which follow upon curvature 
around it, have been persistently misinterpreted. 
In order to obtain the general features of growth-extension, 
a number of developing tendrils of Passiflora coendea were 
marked off at intervals of 1 cm. by means of india-ink and 
a camel’s hair brush. These intervals were re-measured each 
day during the period of nutatory movement and irritability. 
The marks were placed on the convex sides of the organs, 
which were held firmly during measurement by means of 
gelatine-coated clamps in such a manner that they were not 
stimulated. The data obtained are given in the table below. 
The figures expressing the length of the portion or portions 
in the region of maximum growth are given in thicker type. 
By a consideration of the table on p. 380 it may be seen 
that the entire period of development of such tendrils occupies 
from no to 130 hours. The elongation in twenty-four hours 
of certain portions amount to 150 per cent, of their length ; 
the elongation of the entire tendril during the same length of 
time amounts to 20-40 per cent, of its length ; and the 
elongation of the region of maximum growth must have 
greatly exceeded the above rate during the twelve hours 
inclusive of the period of most rapid growth. The com- 
parisons of De Vries of the growtn of the portion of a tendril 
