Bignonia capreolata.—­No organ of any plant, as far as we have seen, bends away so quickly from the light as do the tendrils of this Bignonia.  They are also remarkable from circumnutating much less regularly than most other tendrils, often remaining stationary; they depend on apheliotropism for coming into [page 433] contact with the trunks of trees.* The stem of a young plant was tied to a stick at the base of a pair of fine tendrils, which projected almost vertically upwards; and it was placed in front of a north-east window, being protected on all other sides from the light.  The first dot was made at 6.45 A.M., and by 7.35 A.M. both tendrils felt the full influence of the light, for they moved straight away from it until 9.20 A.M., when they circumnutated for a time, still moving, but only a little, from the light (see Fig. 178 of the left-hand tendril).  After 3 P.M. they again moved rapidly away from the light in zigzag lines.  By a late hour in the evening both had moved so far, that they pointed in a direct line from the light.  During the night they returned a little in a nearly opposite direction.  On the following morning they again moved from the light and converged, so that by the evening they had become interlocked, still pointing from the light.  The right-hand tendril, whilst converging, zigzagged much more than the one figured.  Both tracings showed that the apheliotropic movement was a modified form of circumnutation.

Cyclamen Persicum.—­Whilst this plant is in flower the peduncles stand upright, but their uppermost part is hooked so that the flower itself hangs downwards.  As soon as the pods begin to swell, the peduncles increase much in length and slowly curve downwards, but the short, upper, hooked part straightens itself.  Ultimately the pods reach the ground, and if this is covered with moss or dead leaves, they bury themselves.  We have often seen saucer-like depressions formed by the pods in damp sand or sawdust; and one pod (.3 of inch in diameter) buried itself in sawdust for three-quarters of its length.** We shall have occasion hereafter to consider the object gained by this burying process.  The peduncles can change the direction of their curvature, for if a pot, with plants having their peduncles already bowed downwards, be placed horizontally, they slowly bend at right angles to their former direction towards the centre of the earth.  We therefore at first attributed the movement to geotropism; but a pot which had lain horizontally with the pods

* ‘The Movements and Habits of Climbing Plants,’ 1875, p. 97.

** The peduncles of several other species of Cyclamen twist themselves into a spire, and according to Erasmus Darwin (’Botanic Garden,’ Canto., iii. p. 126), the pods forcibly penetrate the earth.  See also Grenier and Godron, ‘Flore de France,’ tom. ii. p. 459. [page 434]