GERMINATION AND HISTOLOGY OF WELWiTSCHIA MIRABILIS, 15 
On the Germination and Histotocy of the Srnpiine of 
WELWITSCHIA MIRABILIS, By F. Orven Bower, 
B.A., Camb. With Plates III and IV. 
The Mature Embryo. 
Tue development of the embryo of Welwitschia has been 
described by Sir J. D. Hooker, in his monograph on the 
plant (‘ Trans. Linn. Soc.,’ vol. xxiv), and again by Stras- 
burger (‘ Angiosp. und Gymnosp.,’ p. 155). I find the struc- 
ture of the mature embryo to correspond in the main with 
these descriptions, but the embryos, which I have had the 
opportunity of examining, are larger, and possibly better 
matured than those described by the latter writer; while a 
comparison of his fig. 92 with fig. 1° a, 8, c, will show a 
difference of form, as well as of structure. 
I find the mature embryo to consist of a straight radicle, 
with largely developed root cap. ‘To the apex of the radicle 
adheres the suspensor, which, together with the embryonic 
tubes (embryonal-schlaiiche), forms a mass of considerable 
size. Surrounding the body of the embryo may be seen a 
swelling or collar (fig. 1 x). Passing from this towards the 
apex of the embryo, there is a sudden diminution in thick- 
ness, and at a short distance above the collar are borne the 
two cotyledons. From a comparison of fig. 1 A and B, it 
will be seen that the hypo-cotyledonary part of the embryo is 
nearly cylindrical, the cotyledons only being compressed. 
The plane of their compression is that in which the whole 
seed is flattened. A longitudinal section (fig. 1 c) shows 
that between the cotyledons lies the apical cone of the 
plumule. This, as stated by Strasburger, remains undeve- 
loped, as a simple papilla of tissue, up to the time of 
maturity of the embryo. From 2 longitudinal section it is 
seen that the radicle is short in comparison with the root 
cap, and that the latter extends back almost to the thickest 
part of the collar. The epidermis proper, which covers the 
cotyledons and the hypo-cotyledonary stem, loses its identity 
at the point where the root cap begins. From here onwards 
to the apex of the radicle, the external covering is made up 
of a succession of layers of the rootcap. These merge imper- 
ceptibly into the cortical tissue. At the apex of the radicle 
the arrangement of tissues corresponds to the general type 
for the conifere. In Welwitschia, however, the tissues of 
the root cap are more diagrammatically arranged than is 
usual in the group, the regularity of the central series of 
