ADULT ANATOMY OF WELWITSCHIA MIRABILIS. 329 
hypocotyl and no unswollen portion was present (Pl. 34. fig. 6). The meagre develop- 
ment of the hypocotyl in this seedling is probably correlated with the fact that the 
plumular leaves were not properly grown, and were still contiguous by their upper 
surfaces, thus reducing assimilation and retarding growth. 
The top of the fusiform hypocotyl (Pl. 34, X, fig. 2) is slightly flattened between the 
ragged remains of the cotyledons, and it is apparent that some intercalary growth 
must have taken place in this region, separating the once continuous margins of the 
two cotyledonary bases. The method of growth will be more easily understood on 
reference to figs. 1 a and 3, where the downward sloping scars (C) represent the margins 
of the bases of the old cotyledons, now separated from one another by a further growth 
between the cotyledons, resulting in the formation of a more or less triangular portion (T). 
It will be seen that this intercalary growth has taken place just below the swellings (R) 
shown in fig. 1; by means of the upward and lateral growth of these swellings a still 
more noticeable change has taken place, resulting in the development of a very definite 
and swollen ridge continuous round the top of the enlarged hypocotyl. From an exami- 
nation of the intermediate stages referred to (figs. 1a & 3) it is clear that the accelerated 
meristematic growth which first began in the swellings (R) has afterwards spread from 
these swellings round the projecting edge left after the withering of the cotyledons, until 
it forms two elongated ridges which finally fuse in the median plane of the cotyledons 
so as to form a continuous ridge. In fig. 2 a small indentation, at each of the two ends 
of the ridge, is the only sign of its double origin. In many of the older seedlings it 
is found that even this has disappeared (see also O, fig. 9 a). 
Consequent on the upgrowth of this narrow ridge and immediately internal to it 
there is a groove, already of some depth, from the base of which spring the two plumular 
leaves. Between the leaves on their inner side is the depressed apex, which remains 
inactive. On either side of the apex the conical processes, or cotyledonary buds, have 
become considerably enlarged (PI. 34, B, fig. 2); they are much elongated in a plane at 
right angles to the planes of the two cotyledons, a fact which makes ear appearance 
unlike that commonly distinctive of buds, but which is probably to be attributed to the 
effect of lateral pressure, exerted on them during their development by the closely 
appressed plumular leaves. | 
Stage 3.—In fig. 4b it will be seen that the upper par 
become further swollen, so that it is now globular (K). 
even older, were observed in which the fusiform shape was retained, but the globular 
Upper portion has been more or less developed in all the mature plants which have been 
observed. In many seedlings of this stage there is à flattened portion É X, se > 
intercalated by the continuation of growth between the coty ledonary -m is EE 6 
laterally beneath the ridge, but in the seedling shown in fig. ^ there pa s t 
flattened portion developed. The ridge is now still further enlarged, and by sid a 
white appearance is rendered very conspicuous against the rough brown P o ; : 
Test of the hypocotyl. The upward growth of the ridge has and the pes : b 
I$ deepest at its ends opposite the original position of the cotyledons, w | 
nks its floor is raised up by the meristematic division vum tes place 
c3 
t of the fusiform hypocotyl has 
A few seedlings of this age, or 
