Development of ovule, embryo sac, and endosperm in Triteleia (Themidaceae) relative to taxonomy

Six of 14 species of Triteleia were studied. All possess septal nectaries, raphides in the ovary wall, an anatropous and crassinucellate ovule with a micropyle formed by the inner integument only, and parietal cells. A short and thick nucellus, which is not penetrated by the embryo sac, has a one-layered apical epidermis and thickens from its subepidermal layer. The permanently two-layered inner integument is made up of normal, i.e., not greatly enlarged, cells. The embryo sac is of the Polygonum type, and the endosperm is of the helobial type. Embryo development is of the Asterad type in Triteleia laxa and T. ixioides. From an embryological point of view, Triteleia is closely related to Muilla maritima because the two taxa are alike in all characteristics, except for the number of layers in the apical nucellar epidermis. Triteleia is only distantly related to Dipterostemon, Dichelostemma, and Brodiaea, judging from the numerous differences in embryology. Both Triteleia and Muilla maritima are embryologically more primitive than the Dipterostemon-Dichelostemma-Brodiaea group. Embryologically, the Themidaceae are more similar to the Hyacinthaceae than to Allium. However, all embryological similarities with Hyacinthaceae are in plesiomorphic characters.