DEVELOPMENT OF THE SEED AND FRUIT IN MELAMPYRUM NEMOROSUM L. AND M. ARVENSE L.

Abstract

The ovary is bilocular, with four massive axile placentae, each bearing a sessile hemianatropous, unitegmic, and tenuinucellate ovule. The innermost integumentary layer forms endothelium around the micropylar part of the embryo sac. The micropylar canal is surrounded by the micropylar tube, whereas the endothelium is hypodermal in this region. The endothelium and an adjacent meristematic region contribute to the growth of the integument. The endosperm is of the Brunella type described by K. Schnarf in 1929. The chalazal haustorium is a highly aggressive, two-nucleate chamber which becomes inactive and is filled with a haustorial chalazal endosperm. The two multinucleate micropylar haustorial cells give rise to many tubular extensions which pass through the micropylar tube, but only one reaches the placenta. The cells of the storage endosperm are pitted and thickened with hemicellulose. An opaque tanniferous zone of endosperm separates the storage endosperm from the chalazal endosperm. The embryo is small and straight, with two cotyledons and a hypocotyledonary region. The seed coat is feeble, one to three layered. The pericarp is many layered and cuticularized. The two innermost lignified layers form columns at the dorsal line of the two valves of the capsule, where it dehisces. The chalazal part of the developing seed absorbs nourishment directly from the pericarp.