| Abstract: | Engleman , E. Mark . (U. of California, Davis.) Ovule and seed development in certain cacti. Amer. Jour. Bot. 47(6) : 460–467. Illus. 1960.—Ovules of Astrophytum myriostigma, Thelocactus bicolor, and Toumeya papyracantha are crassinucellate, possess a nucellar cap, and have a micropyle formed only by the inner of 2 integuments. Survival of the chalazal megaspore results in a monosporic gametophyte. A single layer of endosperm cells forms a cap over the radicle in a mature seed, as occurs in some of the Centrospermae. The characteristic hilum cup consists of the hilum and variable amounts of thickened cells of the funiculus which border a cuplike cavity. The hilum cup is associated with a funicular hump near the junction of the funiculus and the integuments. The funicular hump is similar in position to a swelling on the funiculus of some members of the Centrospermae. |
