FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 585 
plant represented in fig. 111 and the older plants described and 
figured by Sir J. Hooker. On comparison it will be seen that, 
though the relative positions of the several parts are slightly 
altered by growth, the arrangement of the vascular bundles cor- 
responds to that already described in the younger plant. We 
are able here, as before, to trace a direct vascular connection 
(1) between the leaf and the peripheral part of the stock, (2) 
between the leaf and the crown, and (3) between the stock and 
the crown. It may further he observed how in this older plant 
the central bundles of the stock collect at some distance below 
the entry of the leaf bundles into groups, which are identical 
with the central vascular groups described in the lower part of 
the stock of the younger plant (cf. fig. v1, 4,5). On the other 
hand, the arrangement of the vascular bundles in fig. xt obviously 
corresponds to that described by Sir J. Hooker in older plants. 
We have here (using his nomenclature) the “ vascular stratum,” 
consisting of the bundles which enter from the leaf, the “ ascend- 
ing bundles,” which rise into the crown, and the “ descending ” 
system, which passes into the stock. 
The scheme of vascular arrangement proposed by Bertrand 
(‘Ann. d. Sci. Nat.,’ série v, vol. xx, pl. 12, fig. 14) may be 
here noticed. A glance at the figures illustrating this paper 
will be enough to show that his scheme does not accord with my 
observations. 
In order to confirm our results we may turn to the appearance 
presented by sections taken from an old plant in the plane of the 
bundles of the leaf trace, so as to follow their course into the 
stem (fig. x11). From these it is learnt that the leaf bundles do 
not all run the same distance into the stem; that they vary in 
this respect, some pursuing a direct course almost to the centre 
before they pass out of the plane of section, others successively 
less distances ; also, that there is a certain amount of regularity 
in their arrangement, those which continue their course for a 
less distance in the plane of section alternating with those which 
pursue a direct course for a greater distance. Further, that 
before leaving the plane of section the bundles usually divide, 
and the branches often anastomose with bundles pursuing a 
course perpendicular to them; or they may simply curve out of 
the plane of section without anastomosis, and take a longitudinal 
course upwards or downwards. Lastly, of the bundles, which 
appear cut transversely in fig. x11, while some are connected by 
anastomosis with the bundles of the leaf trace, others appear to 
be quite separate from them; these are the bundles already 
mentioned which pass between the bundles of the leaf trace, and 
maintain a direct vascular connection between stock and crown. 
It will be seen in fig. x11 that fresh bundles running perpendicular 
