Gnetum africanum , with Notes on Gnetum scandens. 1115 
Fig., 11, PI. LXXXVI (01) shows the structure of the free outer integument 
between these two levels. 
The outer zone of the outer integument is traversed by the vascular 
bundles, each of which is accompanied by a strand of parenchyma and 
alternates with strands of tissue composed of isodiametric cells with brown 
indurated walls (Text-fig. 10, B, Text-fig. 11, and Fig. 11, PI. LXXXVI, d). 
Next comes a continuous palisade layer which at the base of the ovule is 
smooth, but in the upper part of the ovule projects outwards and makes an 
angle opposite each bundle. Inside this is the inner fibrous zone, the outline 
of which corresponds with that of the palisade layer. In my oldest ovules 
of G. africanum the palisade and fibrous layers were unlignified from the 
base of the ovule to near the apex, or only very slightly lignified in places, 
but in the mature ovule of G. scandens both layers were lignified throughout, 
and it is probable that there would be more lignification in G. africanum 
when mature. 
As the upper part of the seed is approached the hypodermal strands 
of indurated tissue diminish in size and prominence, while the fibrous 
layer increases. The outward projections of the fibrous and palisade 
layers opposite each vascular bundle become individually more and more 
strongly pronounced, but as the vascular bundles die out the projections 
are also gradually reduced in number, there being always a projection 
opposite each remaining vascular bundle (Text-fig. 11). 1 
When the integument thickens at the apex and clasps the micropylar 
tube the hypodermal strands are lost sight of, and the palisade layer entirely 
disappears. By this time the fibrous layer occupies the greater portion 
of the thickness of the integument and its rays are reduced to four or five, 
opposite some of which the last remaining tracheides of the vascular bun¬ 
dles may still be detected. A characteristic star-like structure (Fig. 16, 
PI. LXXXVII, and Text-fig. 1 r, p. 1116) is thus obtained, which reminds one 
of Ligniers figures of Bennettites and also of Trigonocarpus . At this level 
the radial section of the ovule (Text-fig. 9, p. 1113, Fig. 7, PL LXXXVI, 
and Fig. 15, PL LXXXVII) shows that the ends of the cells constituting the 
fibrous zone have arranged themselves to form a close series of cells 
elongated at right angles to the surface of the integument, and having their 
walls strongly lignified and pitted ; the walls of the inner epidermal cells 
are similarly lignified and pitted (Fig. 7, PL LXXXVI). 
Outside the fibrous zone the expanded portion of the integument 
is composed of parenchyma only, the cells of which show some tendency 
towards arrangement in rows at right angles to the epidermis, though not 
so clearly as in G. Gnemon . 2 The general configuration of this layer 
1 For similar ribbed fibrous layers in integument, see Conosioma (Oliver, 1911), Trigonocarpus 
(Scott, 1907, &c.), and other ancient seeds. A similar tendency to the reduction in number of the 
angles towards the seed apex is seen in Conostoma anglogermanicum, Oliver and Salisbury, 1911, p. 26. 
2 Berridge, 1911, Fig. 1. 
