Consequently the
revolving power is much enfeebled in this species, and under
unfavourable circumstances is completely lost. The shoot must depend
for coming into contact with surrounding objects on the probable,
though not ascertained spontaneous movement of the leaves, on rapid
growth, and on movement from the wind. Hence, perhaps, it is that
the petioles have acquired a high degree of sensitiveness as a
compensation for the little power of movement in the shoots.
The petioles are bowed downwards, and have the same general hook-like
form as in C. viticella. The medial petiole and the lateral sub-
petioles are sensitive, especially the much bent terminal portion.
As the sensitiveness is here greater than in any other species of the
genus observed by me, and is in itself remarkable, I will give fuller
details. The petioles, when so young that they have not separated
from one another, are not sensitive; when the lamina of a leaflet has
grown to a quarter of an inch in length (that is, about one-sixth of
its full size), the sensitiveness is highest; but at this period the
petioles are relatively much more fully developed than are the blades
of the leaves.
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