Development of ovule and seed in Cartonema spicatum R. Br. (Cartonemataceae)

Abstract

In Cartonema spicatum the ovule is completely anatropous and has dermally initiated integuments. The seed coat is formed by the outermost layer of the inner integument and the silicified inner layer of the outer integument, the remaining layers of the last forming a loose cover around the testa. The seed has an operculum (also called embryostega) but no micropylar collar. In these respects Cartonema does not differ appreciably from Commelinaceae, so that the segregation of a separate family Cartonemataceae on seed characteristics alone is unwarranted.