Notes . 
17 1 
and Encephalartos the collaterally-constructed extrafascicular strands 
of the vegetative axis reappear in the more primitive axis of the cone 
as more or less concentrically-constructed strands. The explanation 
of the fact that the second cylinder of the cone is primary, while that 
of the vegetative axis is secondary in origin, may be found in the fact 
that in the former case the strands of the outer cylinder are formed 
quite early, and assume the function of supplying the sporophylls, 
whereas, in the latter case, it is the inner cylinder alone which, in the 
first instance, supplies the leaves, and which goes on developing in 
thickness for some time before the formation of a second cylinder 
is demanded, in order to assist in the general conductive function 
of the stem, and, like the subsequent cylinders, to take a part in 
supplying the leaves. The late period at which the second cylinder 
arises necessitates its earliest beginnings being inaugurated by a cam- 
bium ; but this differing mode of origin cannot in the least affect 
the fact that this ‘ secondary ’ extrafascicular cylinder of the vegetative 
axis is directly homologous with the ‘ primary ' extrafascicular cylinder 
of the peduncle of Encephalartos . Nevertheless, the possibility re- 
mains, which is not improbable, that this latter is equivalent to the 
innermost or primary cylinder of the vegetative stem of the same 
plant, and that the innermost cylinder of the peduncle represents 
an intrafascicular one, such as that existing in the cases above 
mentioned. 
In Welwitschia and the other plants which exhibit it we may regard 
the concentric structure as having been retained in the second cylinder 
of strands, owing to the fact that there has been, in the region where 
they occur, less demand for a modification of the structure to suit 
the strengthening and other requirements of the plant, and it is just 
in those regions of the axis where, a priori , we should expect primitive 
ancestral characters to turn up that they actually do occur. 
I am, of course, aware that the one or two extra rings of bundles 
found in the peduncle and axis of the cone, and which have been 
clearly figured by Strasburger 1 both for Welwitschia and Gnetum (to 
whose striking figure of the cone-axis of the former plant I would 
direct special attention), are of only local and thus transitory occur- 
rence, for they are the strands supplying the flowers axillary to the 
bracts, and in the region of the axis above the uppermost flowers are 
1 Die Coniferen und Gnetaceen, Plate XX, Fig. 49 ( Welwitschia ) ; Plate XXI, 
Figs. 17-22, and 36-7 (Gnetum), 1872. 
3 E 
