Embryogeny and Endosperm Development

Although the process of fertilization was not seen, stages immediately following it were obtained. The youngest pro-embryo was at the three-celled stage. From this it appeared that the first division of the zygote had been transverse, while the next division was a longitudinal one of the basal cell (fig. 20). Irregular division of the apical cells then produced an elongated and finally obovate proembryo without any signs of a true suspensor, but with large basal cells (figs. 21 and 22). Further division produced a globose embryo still without an apparent suspensor, but with light-staining basal cells which may have been the original ones (fig. 23).

An unusual feature, for this family, was the slow commencement of the endosperm; the proembryo had reached a multiple-celled stage before there was any appearance of it. When it did form, the free-nucleate stage was followed quickly by large-celled endosperm with sparse strands of cytoplasm and large nuclei. Endosperm never seemed to fill the entire sac.

Advanced stages of N. menziesii embryos were not seen, but in N. fusca welldeveloped embryos occupied the centre of the sac. They were composed of small cells containing many fat globules. From a central body of tissue two cotyledons were directed towards the micropylar end of the sac and a broad radicle was directed towards the antipodal end (fig. 25).