Seed external morphology and coat anatomy of ten species of tribe
Asclepiadeae (Asclepiadoideae-Apocynaceae) in Egypt are investigated using
Light Microscope (LM) and Scanning Electron Microscope (SEM). Seed
features studied include variations in shape, colour, texture, hilar details,
surface scan characteristics and seed coat anatomy. Anatomically, the testa
has been found to be of greatest value in determining taxonomic relationships.
Some seed characters were found to be very distinct at the generic level, such
as the presence of two rows of the palisade-like cells of the seed wing (one
upper and one lower) which could be considered as taxonomic marker for the
two Pergularia species. In addition, the presence of mounds on the upper
concave side of the seed coat is recorded only in two Asclepias species and
Solenostemma arghel; with large, tubular, lignified, pitted cells in two
Asclepias species, and small, rectangular, radially elongated in Solenostemma
arghel.