Notes. 
767 
xylem, Hence, there is found in the foliar organs of these female 
inflorescences what I regard as a relic of the more primitive structure 
of the older types of Coniferae and of the Cycads, and which is 
not found in the vegetative foliar organs cf the plants concerned. 
The male sporophylls (on the view which I prefer taking of them) 
of the three genera are constituted according to the radially - 
symmetrical type. In Ephedra they are grouped intimately together 
so as to form a single columnar structure bearing the pollen-sacs 
at the apex. In Welwitschia they are fused, at least at the base, three 
and three together, into two groups on opposite sides of the flower. 
In Gnetum two sporophylls are intimately united together to form, 
as in Ephedra , a single column. In accordance with the radial or 
cylindrical structure the vascular bundle of the sporophyll in all three 
genera consists of what I must regard as a reduced concentric structure 
of which only the few small, central, spiral tracheides, forming a 
circular group, remain, the phloem being absent or quite undistinguish- 
able from the surrounding parenchymatous tissue. In this structure 
of the sporophyll we find a primitive type, which has been lost in 
Coniferae and modern Cycads, but which occurs in the fossil genus 
BennettiteSy as also in Ginkgo 1 . It is remarkable that this ancient 
type of sporophyll, with its corresponding vascular structure, should 
have been preserved in the otherwise advanced group of the Gnetaceae. 
In the peduncle and axis of the female ‘ cone ’ of Welwitschia 
a most interesting structure obtains. The bundles of the innermost 
ring or central cylinder, twenty-five or so in number, frequently have 
an inverted strand attached to their dorsal side ; the same phenomenon 
precisely which I have observed in the peduncle of some Cycadean 
cones 2 ; this inverted strand may sometimes be so fused laterally with 
the main strand as to form a concentric structure of which the phloem 
occupies the centre. But the most remarkable part of the whole 
structure consists in the presence of a number (about twelve) of rather 
widely-separated strands which belong for the most part to the 
concentric type of structure, although in reality only some two or three, 
in any one transverse section, possess this structure in perfect form, 
the others being more or less curved or horse-shoe-shaped ; or, again, 
1 Worsdell, * The Affinities of the Mesozoic Fossil Bennettites Gibsonianus 
Carr.’ Ann. Bot., December, 1900. 
- The Vascular Structure of the Sporophylls of the Cycadaceae. Ann. Bot., 
vol. xii, 1898, Plate XVII, Figs. 2 and 4. 
