The Embryo Sac and Embryo of Striga lutea

Abstract

1. Striga lutea is a semi-parasitic annual belonging to the Rhinantheae-Gerardieae group of the Scrophulariaceae. 2. The ovary is of the ordinary bilocular scrophulariaceous type, and the ovules are anatropous, with one integument. 3. The megaspore mother cell arises directly from a single subepidermal cell, which gives rise to a row of four megaspores, of which the lowest develops into the embryo sac. 4. The 8-nucleate embryo sac develops in the normal way, and at the time of fertilization contains two synergids, an egg, the fused polar nuclei, which lie in the upper part of the sac, and three antipodal cells, which show signs of disintegrating. 5. Double fertilization occurs. 6. Endosperm is formed by cell division. From the chalazal end a long binucleate haustorium is formed, penetrating the integument. The micropylar haustorium is inconspicuous, simply consisting of a few ordinary endosperm cells with fairly dense contents. 7. The proembryo has a long suspensor of three or four cells. The basal cell of the suspensor forms tuberous haustoria. 8. The mature embryo is of the usual dicotyledonous type and is surrounded by one thick-walled layer of endosperm cells. 9. The testa consists of one layer of lignified cells which are admirably suited to protect the young embryo.