Embryology and Reproductive Ecology of the Darling Lily, Crinum flaccidum Herbert

Abstract

In Crinum flaccidum the anthers are versatile and tetrasporangiate with a secretory tapetum of binucleate cells. Successive cytokinesis in microspore mother cell results in isobilateral and decussate microspore tetrads. The mature pollen grains are single, spheroidal, disulculate, echinate and 2-celled. In the mature anthers, fibrous thickenings develop not only in the endothecium but also in two or three middle cell layers and the connective tissue before latrorse dehiscence. A lobed tissue in each of the three locules of the ovary serves ovular and placental functions. Each extension of the 5-7 paired lobes represents an ategmic ovule. The development of the female gametophyte conforms to the Polygonum type. Usually only one gametophyte is present in each lobe but occasionally several may occur. Bulb growth is monopodial with normally three umbels produced per plant, each carrying an average of 10 flowers, only two or three of which are open at any one time. Nectar sugar concentration was measured at 14.2% (w/w), of which 44.8% of solids was sucrose and 3.9% either glucose or fructose. The protandrous flowers are phalenophilous, pollinated by sphingid moths. The endosperm formation is of the nuclear type. In the absence of seed coats and the nucellus at maturity, the outer layers of the endosperm become corky following the activity of a phellogen. Embryogeny appears to be of the Asterad type. The mature embryo is straight and chlorophyllous. The large (5.3 g) seeds are 89% water and show no dormancy, germinating without an external supply of water, sometimes while still on the parent plant.