Plant stalk

Usage examples of peduncle.

At the base of the peduncle there is a mass of small cells, forming a welldeveloped pulvinus, which is exteriorly coloured purple and hairy.

The inferior peduncles are the corpora restiformia, previously described, and consist of both sensory and motor filaments.

Whilst the perfect flowers are thus bending down, the whole peduncle curves downwards and increases much in length, until the flowerhead reaches the ground.

Any one who will observe a flowerhead burying itself, will be convinced that the rocking movement, due to the continued circumnutation of the peduncle, plays an important part in the act. Considering that the flowerheads are very light, that the peduncles are long, thin, and flexible, and that they arise from flexible branches, it is incredible that an object as blunt as one of these flowerheads could penetrate the ground by means of the growing force of the peduncle, unless it were aided by the rocking movement.

We therefore protected some flowerheads, similarly secured to sticks, from the light, and although some of them rotted, many of their subpeduncles turned very slowly from their reversed or from their horizontal positions, so as to stand in the normal manner parallel to the upper part of the main peduncle.

Considering that the flowerheads are very light, that the peduncles are long, thin, and flexible, and that they arise from flexible branches, it is incredible that an object as blunt as one of these flowerheads could penetrate the ground by means of the growing force of the peduncle, unless it were aided by the rocking movement.

These taken together suffice to render it probable that all peduncles and subpeduncles circumnutate whilst growing.

With these facts before us, bearing also in mind that the tendrils of not a few plants consist of modified peduncles, we may admit without much doubt that all growing flowerstems circumnutate.

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.

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.

The pot, in the same position, was next brought back into the light, and after two days there was some bending downwards of the peduncles, and on the fourth day two of them pointed to the centre of the earth, as did the others after an additional day or two.

This pot was then brought back into the light, and after three days the peduncles were considerably bowed downwards.

Considering the great length and thinness of the peduncles and the lightness of the pods, we may conclude that they would not be able to excavate saucerlike depressions in sand or sawdust, or bury themselves in moss, etc.

As this latter movement occurred in complete darkness, and with peduncles arising from upright and from dependent branches, it cannot be due to apheliotropism or to epinasty, but must be attributed to geotropism.

Three very young peduncles had as yet moved only a little downwards, but after an additional 24 h.