10 DR. J. D. HOOKER ON WELWITSCHIA. 
Towards its upper part, close under the base of the leaf, the circumference of the stock is 
marked more or less obscurely or deeply by concentric furrows, separating convex ridges, 
that repeat as it were the ridges of the crown: these are best seen in Plates IV., V., & XI. 
fig. 1, where they extend far down the stock. On the upper or outer of these ridges of 
the stock a few pits occur, in which flower-buds are occasionally developed; and, as it 
would appear, the latter sometimes arrive at maturity; for in one specimen I find the 
bases of three old peduncles in situ. In Mr. Andersson’s large specimen there are four 
of these pits, vertical, superimposed on the four uppermost ridges of the stock. This 
may be regarded as an anomaly, to which I shall again allude when treating of the 
development of the plant. 
The texture and appearance of the surface of the stock vary at different positions 
and ages: in the oldest specimens (Plates III., IV., & V.), it is uniformly hard, brown, 
rugged, and traversed by longitudinal fissures extending through the periderm; the 
ridges here extend but a little way below the leaf, and the superficial tissue of the peri- 
derm is broken up into isolated, distant, angular masses (Plate III.), denoting the great 
increase of the subjacent tissues. The superficial tissues of the ridges are always 
smoother and lighter-coloured than those of the rest of the stock; and in Monteiro’s 
and Andersson’s fresh specimens these parts are some of a pale yellow-green colour, and 
others of a bright green, and were still in a living state on their arrival. 
The gummy substance (a true collenchyma) which exudes in large tears from the 
stock and other parts will be noticed when describing the internal anatomy of the stock. 
oot.—This varies in my specimens from 1 to 2 feet in length; it is, as I before 
observed, either continuous with the stock, or else the latter terminates abruptly above 
it; it is slightly twisted, either nearly cylindrical, or if compressed, not so much so as 
the stock, although parallel to it; it gives off few fibres anywhere, and branches chiefly 
towards the base—indicating that the upper stratum of soil is extremely dry. Super- 
ficially it is of a much darker colour than the stock, being sometimes quite black; and 
the periderm peels off in places as a distinct bark. Owing to the nature of its tissues, 
the root is somewhat flexible. 
Anatomy of Trunk. (Plates XI. & XII.) 
A vertical section through the axis of a plant of Welwitschia exposes the following struc- 
ture: 1. a brown cortical layer or periderm ; 2. a largely developed parenchyma, of which 
the mass of the plant consists; 3. a fibro-vascular system of a very anomalous character. 
Periderm.—This invests almost the whole plant with a very hard layer, of variable 
thickness and undefined boundary ; it is most developed over the crown and towards the 
lower part of the stock, where it attains a thickness of À to 3 of an inch in the largest 
specimen, becoming thinner and finally disappearing towards the insertion of the leaf; 
it is absent from the inner surfaces of the groove enclosing the base of the leaf. Its 
colour is a dark brown on the crown and stock, and almost black on the root; it is 
much the hardest on the crown, which is probably owing to the action of the sun’s rays 
in the arid climate which the plant inhabits. The outer surface of this periderm cracks 
extensively as the plant grows, chiefly longitudinally on the stock, and radially on the 
