The epidermis on the dorsal side is interrupted by stomata
and is feebly cutinised (Fig. 5a). These epidermal cells are polygonal
in an aerial view (Fig. 1e and f) but are almost rectangular
in cross section (Fig. 5a). The upper epidermis almost completely
lacks chloroplasts which are otherwise prominent in the lower
epidermis and in the ventral parenchymatic cell layers (Fig. 5a).
The cells of the growing pseudoroot depict high number of chloroplasts
(Fig. 5a). On the dorsal surface, below the stomata are the
prominent sub-stomatal air spaces (Fig. 5a and b). The frond is
multilayered atthe centre composed of loosely arranged parenchymatous
cells interspersed with air spaces towards the dorsal side
and of more tightly packed parenchymatous cells with small air
spaces towards the ventral surface (Fig. 5a). It tapers to a one cell
thick outer rim (Fig. 5a). The cells of the growing pseudoroot are
also housed with considerable amounts of starch grains in their
plastids (Fig. 5a). Itis tempting to speculate thatthese may function
as statoliths for the positive geotropism in the growing phase ofthe
pseudoroot. There is no hint of any vascular tissue differentiation
(Fig. 5a).
The meristematic initial of the pseudoroot starts appearing
when the frond is very young and still connected with its
mother (Fig. 5b). These well-staining small cells seem to be in
a tunica-corpus like arrangement characteristic of the shoot apical
meristem, with the differences that: (1) no lateral primordia
appear, (2) no vascular tissues develop, and (3) the pseudoroot
shows a positive geotropism. Subsequently, this apical meristem
differentiates almost fully into epidermis and parenchyma,
so only a layer consisting of a few cells remains (Fig. 5a and
c). This may terminate the growth of the pseudoroot. Apart
from the tip, the pseudoroot consists of 6–10 parenchymatous
cell layers without any specialization (Fig. 5c). The epidermis
of the pseudoroot is in continuation with that of the floatingflattened part of the frond and the cells constituting the inner
layers are also in continuation with the corresponding inner
regions (Fig. 5a). The cells close to the flattened part are elongated
(Fig. 1i) and the ones to the tip are much smaller and roundish
(Figs. 1h and 5c).