io8i 
Relationships of the Gnetales . 
the continuous thickening of the girdle would indicate that this was 
originally the case. But as a rule it may be said that the leaf-traces 
are organized from the ring of nodal wood. 
Another species possessing this organization of the primary vascular 
bundles is E . vulgaris. In E. trifur ca the leaves are in whorls of three, so 
that in each internode there are three pairs of large bundles alternating 
with three pairs of small ones. The girdle and traces, however, are usually 
organized in the same way as in E. distachya and E. vulgaris. Occasion- 
ally, however, the intercalary bundle between the two strands of the leaf- 
trace is absent. Such a trace with its two strands leaving the stele side by 
side is photographed in Fig. 6. The condition here is similar to that 
of other plants which have the double leaf-trace. It is no doubt the primi- 
Text-fig. 2. E. altissima. Reconstruction of course of primary fibro- vascular bundles. 
tive condition, for it obtains exclusively in the traces to the reproductive 
bracts. 
A more complicated condition of the whole primary system is found in 
such species as E. altissima. Text-fig. 2 is a reconstruction of the bundle 
course in this species. As the leaves occur in whorls of three, the internode 
has three pairs of large bundles alternating with three groups of smaller 
ones. But in this case each of the smaller groups contains three bundles 
instead of two. Accordingly the total number of bundles is fifteen. The 
nodal ring is organized in the same way as before. The most striking 
difference is that the strands of the leaf-trace arise, not above the small 
bundles of the internode, but above the spaces between them. The inter- 
calary bundle is then directly above the central small bundle of the group, 
and the traces arise over the spaces which separate the central bundle from 
its fellows. In this case, at least, the traces cannot be considered as con- 
tinuations of the internodal bundles. In addition to the origin of the leaf- 
traces, the most striking difference is the presence of three small bundles 
4 B 
