![Thumbnail: [Volume 80, 1952 page 212]](/journals/rsnz/images/rsnz_80/thumbnails/rsnz_80_02_0396_0212_ac_02.gif)
The Mature Seed
By the time the seed fell the cotyledons, radicle, and plumule completely filled the nuts. All trace of endosperm had disappeared and the integument had been absorbed except for the outermost layer of cells. Thus an exalbuminous nut was formed in which the cotyledons were folded in a corrugation (fig. 29). This method of folding is the same as that found in Fagus. Blume (1850), in erecting the genus Nothofagus, and Oersted (1873), in cataloguing the differentiating characters of Fagus and Nothofagus, stated that the cotyledons of Fagus were folded like a corrugation and those of Nothofagus were folded flat. In the New Zealand species of Nothofagus, however, the cotyledons are corrugated.
In the species N. fusca, N. truncata, N. solandri, and N. menziesii the seed was physiologically ripe at seed-fall, for, under suitable conditions, germination took place shortly afterwards.
Mature nuts show the following structure in cross-section (figs. 27 and 28): Pericarp:
| (a) |
An epidermal layer of small, regular cells from which arise sparse, short, unicellular hairs. |
| (b) |
A thin, parenchymatous layer, five to six cells deep, of small, regular cells. This layer is irregularly folded in places. |
| (c) |
The hard “wall” of the nut composed of a layer of fibres averaging seven to eight sclerenchyma cells wide, the fibres arranged longitudinally in cross-section. |
| (d) |
A thin-walled, single layer of cells lining the cavity of the nut. |