598 Dutkie I — Anatomy of Gnetnm africanum. 
Cork. The formation of cork in the internodes of G. africanum was 
found to be very irregular. The phellogen originates in circumscribed 
areas of the stem epidermis (the dots and striations mentioned above) 
and then spreads peripherally (PI. LVIII, Fig. 21). It is not unusual to find 
part of an internode covered with 8-10 layers of cork and the rest with no 
sign of phellogen formation. This is probably connected with the climb- 
ing habit of the species. Some of the older internodes are surrounded 
by a thin and regular mantle of cork whose surface shows many minute 
cracks. In several of the stems examined, however, periderm formation 
cuts deeper and deeper into the cortex at certain points, and thus cor- 
tical fibres and secretory tubes come to be embedded in the outer cork. 
Occasionally, groups of fibres are completely isolated by cork cells 
(PI. LVII, Fig. 4). In longitudinal sections these cork rings are found to be 
connected with the peripheral layer of cork. Similar cork rings surrounding 
a core of fibres were found in G. scandens and G. Buchholziajium . Layers 
of thick-walled phelloderma cells containing numerous crystals are some- 
times found inside the phellogen. In several internodes the ground tissue 
cells inside the sclerenchymatous zone were found to have undergone 
division, often to such an extent that part of the zone of stone cells was 
ruptured and pushed out to the periphery of the stem, while large paren- 
chymatous cells next to the phloem masses had become sclerosed. If an 
anomalous zone of xylem and phloem occurs in this species, the cambium 
must arise in this secondary tissue inside the zone of sclerenchyma (PL LVIII, 
Figs. 19, 30). A curious feature of some of the sections examined was the 
mucilaginous disorganization of groups of parenchymatous cells in the region 
of the protophloem masses (Fig. 20). 
Stem Apex. According to Stapf, 1 Dingier 2 made the surprising 
statement that he had traced the growth of the stem apex of Ephedra 
to a 4-sided apical cell. Microtome sections were cut through the apical 
cone of branches of G. africanum , but in every case a small-celled meristem 
was found. 
Leaf. 
As was mentioned above, G. africa?ium possesses pairs of scale 
leaves in addition to the expanded foliage leaves. In transverse sections of 
the node below the swollen bases of the foliage leaves, eight bundles are seen 
to leave the stele, four passing into the base of each leaf. The two median 
leaf-traces are the first to separate from the vascular ring (PI. LVII, Fig. 5). 
Sections through the bases of the pair of scale leaves immediately below 
the female cone showed the same bundle supply. On tracing the bundles 
through the scale leaf they were seen to fuse laterally, so that near the 
apex the separate strands could no longer be distinguished. A small twig 
which possessed six pairs of scale leaves was also examined. The vas- 
cular supply resembled that described above. Undeveloped buds were 
1 Stapf (7). 2 Dingier (4). 
