An Ecological Study of Alstonia Venenata R.Br. (Apocynaceae: Rauvolfioideae) and Cryptolepis Buchanani R.Br. Ex Roem. & Schult. (Apocynaceae: Periplocoideae)

Abstract

_Alstonia venenata_ and _Cryptolepis buchanani_ belong to Apocynaceae family. The two species with shrubby habit occupy different locations but both bloom during summer season. _A. venanata_ flowers are milky white and very prominent during forenoon period. The relative positions of floral sex organs facilitate the occurrence of autonomous autogamy. Butterflies and honey bees visit the flowers during forenoon period only when the former collect nectar while the latter collect pollen but both act as pollinators. The fruit production rate in this species is a result of autognomous autogamy and vector-mediated self- and cross-pollination. _C. buchanani_ flowers are greenish-yellow, nectariferous and unattractive to the flower visitors present in that area. The low fruit production rate in this species is exclusively a result of autonomous autogamy. Fruit is a paired follicle in both plant species and each follicle produces several to numerous seeds according to the production rate of ovules in flowers. Follicles shed seeds when dry and the seeds thus liberated are dispersed by wind and hence both _A. venenata_ and _C. buchanani_ are anemochorous.