273
ON THE PROTANDRY OF THE FLOWERS OF
AESCHYNANTHUS HOOKERI, CLARKE
BY
M. 0. Tirunarayana Iyengar, B.A., F.Z.S.,
Entomologist Department of Public Health , Bengal , {Calcutta.)
The flowers of Aeschynanthus Hookeri Clarke (PL II.) were studied with reference to an interesting form of floral protandry. This species is very common on trees in the Darjeeling district from 4,000 to 8,000 feet above sea-level. It has very fleshy leaves, green above and yellowish green below, opposite, lanceolate, acuminate, very feebly serrate and obscurely nerved. The plants hang pendulously from the branches of trees and bear bright red flowers in terminal clusters. The calyx is long, tubular and 5-fid at tip. Corolla tubular, slightly bi-labiate and hairy. Stamens four, didynamous, the anthers of the upper pair fusing by their tips and so also those of the lower pair ; anthers, oblong and opening by slits on the under side. Ovary superior.
In the bud, the stamens are well-developed, with stout oblong anthers ; the pistil is very small, the style being much shorter than the ovary. When the flower opens the two pairs of stamens are well developed and are exserted to nearly an inch beyond the corolla tube ; but the pistil is still very short and undeveloped. After the flower opens, the style grows and elongates rapidly and after three to four days reaches the mouth of the corolla (Pl. I. figs. 1 and 2). Its growth continues and after a few days more the tip of the style reaches the same position as the longer pair of stamens occupied when the flower opened (PL I. fig. 3). Th8 stigma then gets well developed and at the same time the two pairs of stamens move ventrally and finally curl over the lower lip of the corolla (PL I. fig. 4).
This remarkable example of protandry is apparently helpful in preventing self-pollination. It is in some ways similar to the protandry of the flowers of the Genus Clerodendron . In Clerodendron , the stamens ripen first and the stigma subsequently. When the flower opens the mature stamens project beyond the upper lip of the corolla while the style occupies a ventral position and curl over the lower lip of the corolla. When the anthers have opened and begin to shrivel the stigma ripens and the style and the stamens then change places ;
