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PROFESSOR MACAIRE ON THE DIRECTION ASSUMED BY PLANTS. 
The tendril of the Tamus is very smooth, and its surface contains neither resinous 
nor glutinous matter, nor hair of any kind. When slightly rubbed between the 
fingers, it does not contract itself. To obtain its curling up, it is necessary that 
the contact should be only on one side. If the solid body round which the tendril 
had begun to coil be removed, it continues to contract itself in the air, but without 
fastening the knot on itself, the empty ring remaining constantly open. If, after a 
little time, an object of suitable size and form be introduced in this empty ring, it 
contracts anew and the knots tie themselves firmly on this new body. 
If the tendril be left without internal support after its contraction, it does not turn 
again, nor resume its primitive direction in a straight line ; on the contrary, the con- 
tractions are soon extended over the whole of the tendril so as to give it the appear- 
ance of a corkscrew. 
The same thing happens to those tendrils the extremities of which are attached to 
a supporting body. This arrangement has the effect of preventing the tearing of the 
tendril when the plant is shaken by the wind, by giving it the shape and elastic pro- 
perties of an helicoidal spring {ressort a houdin). 1 placed a small portion of a branch 
in contact with a tendril of Tamus ; when it had begun to contract itself and the first 
knot had been tied, I let the branch go and it remained suspended. Not only did the 
tendril support the weight of the branch, but it continued to roll itself up around it, 
raising it more and more by each knot. Ten rings were thus formed around the slip, 
regularly arranged in a spiral by the side of each other. The branch was entirely 
covered over by them, and as there was no room for more, the tendril continued to 
contract itself in the air towards its base, and to form empty rings in the form of a 
corkscrew, having nearly the same dimensions as those on the branch. 
When a body, such as an iron rod, too heavy to be supported, is placed in this 
way, the knot formed becomes loose and the rod drops. If the tendril rolls itself 
round a body that is soft and not elastic, such as a piece of packthread, it presses it 
tightly enough to render its diameter visibly less in the part where the knots are 
tied. This pressure may even be rendered sensible to the touch if the knot be suffered 
to form round the finger, and it goes on increasing to a certain extent. 
When the tendril lays hold of an elastic body having a conical shape, such as the 
flat part of a leaf rolled up in a funnel, the knots slide over the leaf as they are formed 
and suffer it to escape. When a tendril of Tamus has begun to curl near its extre- 
mity and to fasten itself round any object, if the upper portion of the same tendril 
chance to meet with another exciting body, another part of the same branch for 
instance, it may curl over again in a spiral at this point and tie its knots there. The 
same thing may happen a third time; and in this way may be seen in the same tendril 
two or three portions closely wound round an object, while the remaining part of the 
tendril is loose and detached. The contraction of the tendrils of the Tamus always 
takes place in the same direction, and the curling is turned inwards, whether there be 
or be not an object round which it may occur: and more than this, when a round 
