The Round-Headed Rampion
(PHYTEUMA ORBICULARE)
In England we have only two kinds of Rampion and both are rare, but in Switzerland there are no less than ten different species, with blue and white flowers, and some of them are extremely abundant. One of the commonest of the blue-flowered varieties is here photographed. It grows in mountain pastures and poor meadows between 3000 and 8000 feet, and is found not only in the Alps but all over Central Europe, though absent in the North. It flowers in July, and the size of the plant undergoes considerable variation according to the altitude at which it grows. Sometimes the flower-stalks are but 3 or 4 inches long, at others 16 or 18. The leaves, which grow from the root stock, have serrated edges, and are frequently a good deal larger than those of the specimen photographed. The methods adopted by the plant for the distribution of its pollen and the fertilisation of its seeds through the agency of insect visitors are of particular interest. Each flower of the flower-head is formed of a blue tubular structure (corolla), which is at first closed above. In the centre of this is the style covered by short hairs and surrounded by the five stamens. While still in the bud the stamens shed their pollen, which collects in the tube around the style and is retained in position by the short hairs. Now the flower opens at its tip, and while maintaining its tubular character above splits longitudinally below into five or six segments, so that linear openings are formed. The result is that when an insect settles on the flower the tubular corolla is very easily depressed, exposing the style surrounded on all sides by pollen. Any pollen that is not removed by the insect falls from the style, for the short hairs on the style by which it is held in position very soon fade. The style then splits above into three segments, exposing for the first time the sticky stigmatic surface now ready for pollination.
The Round-headed Rampion is one of the five Swiss species with rounded, not elongated, flower-heads. Three of them can at once be put aside, because they are usually much smaller plants and have less than twelve flowers to a flower-head, whereas the Round-headed Rampion has always more. Phyteuma Scheuchzeri is distinguished from this plant by its lilac flowers, longer stalked and usually broader basal leaves, and especially by the circle of leaves immediately beneath the flower-head, which are longer than the flowers themselves.
Plate XXV.
PHYTEUMA ORBICULARE. L.
The Round-headed Rampion. Raiponce à Capitules Arrondies. Kugelköpfige Rapunzel.