Development of the Ovule and Megagametophyte in Saxifraga hieracifolia

Abstract

Wiggins, Ira L. (Stanford U., Stanford, Calif.) Development of the ovule and megagametophyte in Saxifraga hieracifolia. Amer. Jour. Bot. 46(10): 692–697. Illus. 1059.—Buds of Saxifraga hieracifolia collected in the vicinity of Point Barrow, Alaska, fixed, sectioned, and stained by standard methods, revealed that the archesporial cell in the ovule of this species is hypodermal and gives rise to the megaspore mother cell and a small number of parietal cells. Occasionally 2 megaspore mother cells occur within an ovule. Meiosis in the megaspore mother cell produces a linear tetrad of megaspores, the chalazal one of which normally gives rise to a monosporic, Polygonum-type megagametophyte. The polar nuclei fuse near the chalazal end of the megagametophyte and the antipodal cells disintegrate prior to fertilization. A distinct filiform apparatus and a marked lateral “spur” develop on each synergid. Vacuolation in the egg cell and in the synergids follows the usual pattern. Only a single integument surrounds the nucellus.