Studies in the embryology ofSenecioneae (Compositae)

Anthers are tetrasporangiate inEmilia sonchifolia andNotonia grandiflora and bisporangiate inGynura nitida. The male archesporium consists of a single row of 6–8 hypodermal cells. Development of anther walls is according to the Dicotyledonous type. The tapetum corresponds to the periplasmodial type. Both tetrahedral and isobilateral pollen tetrads are produced. The pollen grains at the time of anther dehiscence are three-celled inG. nitida andE. sonchifolia;N. grandiflora is male sterile. All the three species have Polygonum type embryo sacs with variable antipodal cells. InG. nitida andE. sonchifolia fertilization is porogamous, endosperm development is of the cellular type, and embryo development closely follows that ofSenecio vulgaris (Souèges 1920a, b).