Page:On the Various Contrivances by Which British and Foreign Orchids are Fertilised by Insects, and on the Good Effects of Intercrossing.djvu/54

little upwards; and this seems well adapted to drop the pollen-masses into the deep stigmatic cavity over a ledge in front. The difference between the first elastic and the second or reversed hygrometric movement, was well seen (I tried it only in the Oncidium) by placing the pollinium, after both movements had taken place, into water, when the pedicel moved into the position which it has at first acquired by elasticity, which latter position was not in any way affected by the water. When taken out of the water the hygrometric movement of depression soon recommenced.

In Rodriguezia secunda there was no slow movement of depression in the pedicel as in the before-mentioned R. suaveolens, but there was a rapid downward movement, due, apparently, in this one case, to elasticity; for when the pedicel was put into water it showed no tendency to recover its original position, as occurs with all the many other Orchids which I have examined.

In Phalænopsis grandifiora and areabills the stigma is shallow and the pedicel of the rostellum long. Consequently a compensating action is requisite, which, differently from the case of the Maxillaria, is effected by elasticity. There is no movement of depression; but, when the pollinium is removed, the straight pedicel suddenly curls up, thus (.--^--). The full-stop on the left hand may represent the balls of pollen, but the disc on the right hand must be imagined to be a triangular piece of membrane. The pedicel does not straighten itself in water. The end carrying the balls of pollen after the contraction is a little raised up, and the pedicel, with one end raised, and with the middle part upwardly bowed, seems well adapted to drop the pollen-masses, over a ledge in front, into the deep stigmatic cavity.

In Calanthe Masuca and the hybrid C. Dominii the structure is very different. We here have two oval, pit-like stigmas standing quite laterally on each side of the rostellum (Fig. XXIV.). The viscid disc is oval (Fig. B) and has no pedicel, but eight masses of pollen are attached to it by very short and easily ruptured caudicles. These pollen-masses radiate from the disc like the spokes of a fan. The rostellum is broad and its sides slope on each side towards the lateral pit-like stigmas. When the disc is removed the rostellum is seen (Fig. C) to be deeply divided in the middle. The labellum is united to the column almost up to its summit, leaving a passage (n, A) to the long nectary close beneath the rostellum. The labellum is studded with singular, wart-like, globular excrescences.