92 - THE VEGETABLE WORLD. 
two folioles. He was thus able to state what direction it took in 
retiring from the fixed indicators. He soon observed that the 
summit of the petiole described an ellipsoide curve in the air 
while the tendril which terminated it had various motions. He 
soon observed that the. internode of this leaf participated in this 
movement of revolution, and that it was even the principal agent 
in it. The merethale or internode and the leaf then produced: by 
their general movements a sort of cone, whose summit occupied 
the lower part of the metherale, and whose base was the curve 
described in the air by the summit of the petiole. The tendril, 
during the movement of revolution, constantly described its point 
towards the bottom of the chamber, thus shunning the light, 
turning itself when the movement of its revolution in leading its 
point near the window tended in the direction of the light. 
‘This revolution was effected in a period varying with the 
terhperature and the age of the leaf. It lasted from an hour to 
twenty minutes at a temperature of 24°; from seven to eleven 
hours when the temperature was lowered to 5° or 6°. The extent 
of the revolutions diminished in proportion as the temperature 
decreased. ‘ What is the cause of this revolving movement a 
asks Dutrochet. ‘It is not revealed to our eyes. It is some vital 
and internal exciting cause. Not only does the light contribute 
nothing towards the production of the movement, but it operates 
against it, and when unusually vivid it seems to stop it.” 
Dutrochet observed the movement of revolution in the tendril of 
the Bryone, and also in the cultivated Cucumber. In the Bryone 
- the tendril moved in very varied directions, sometimes moving 
horizontally, sometimes upwards, sometimes downwards, and some- — 
times directing its points towards the heavens, then taking any 
curve whatever in order to take immediately a curve in the 
contrary direction. The tendrils of the cucumber moved like the 
hands of a watch placed on the dial plate, directing its points 
successively towards every point of the compass, sometimes to the 
right, sometimes to the left. But it defied all the sagacity, all the 
quick and deliberate observation of Dutrochet, to discover the slow 
and obscure movements of which we speak, or their origin. 
The spontaneous movements which we have now to note In 
certain vegetables, are much more apparent. Let us speak first . - 
