D S End "etn 
ente iei ees pees Sed a on cr ERR aes 
46 DR. J. D. HOOKER ON WELWITSCHIA. 
Fig. 19. Another embryo-sac, with pollen-tube attached, and suspensor forming; the second series of 
cells here being developed. | 
Fig. 20. Cone of the nucleus removed, showing pollen-grains on its apex ; eight impregnated secondary 
embryo-sacs, with their bases sheathed in the apices of their suspensors; between these the 
bulbous bases of the unimpregnated secondary embryo-sacs are seen. 
Fig. 21. Base of cone from another ovule, with bases of many unimpregnated secondary embryo-sacs and 
four impregnated ones, of which two are cut off, one apparently aborted, and the fourth 
sheathed by the upper cells of the suspensor. 
Fig. 22. Base of impregnated secondary embryo-sac after elongation, showing the lobed germinal vesicle 
and contracted base of the sac. 
Fig. 23. The same further advanced, the lobes of the upper part of the germinal vesicle having given 
rise to six incipient cells above it. 
Fig. 24. The same, with the cells above the terminal one developed and elongating, showing also the attenu- 
ated tubular base of the secondary embryo-sac retiring, as it were, from the terminal cell. 
Fig. 25. Apex of a suspensor when nearly fully developed, but before the embryo commences to grow ; 
showing the great accumulation of cells, of which the outer are gradually smaller, free wholly 
or in part, and often recurved. 
Fig. 26. First series of cells of a young suspensor, torn away from the terminal cell. 
Fig. 27. Attenuated base of an impregnated secondary embryo-sac, exposed by the removal of all but 
two of the upper sheathing-cells of the suspensor. 
(All the above are very highly magnified figures.) 
PraATrE XI. Vascular system of trunk (p. 13). 
Fig. 1. A longitudinal section through the middle of both leaves of a full-grown but small specimen, 
reduced to about one-half; showing, to the right, the insertion of a peduncle and a bud; the 
deep groove in which the leaf-bases are inserted; the principal vascular stratum running 
across the trunk, parallel to the surface of the crown ; the ascending vascular bundles in the 
crown, the descending ones in the stock, and the indefinite bundles in the axis and root. 
Fig. 2. Transverse section of one of the lobes of fig. 1, taken at right angles to the plane of the cut surface; 
of the natural size. "This section cuts through each vascular bundle of the principal vascular 
stratum in its course from the leaf-base to the axis of the plant. 
Fig. 3. A longitudinal section of a portion of the stock, taken through the centre of the depression of 
fig. 1 (that is, between the bases of the leaves), of the natural size. This section shows how 
confused the vascular bundles are in the stock, towards the contiguous bases of the leaves, 
and that those in the crown pass inwards, parallel to the surface. 
Fig. 4. Transverse sections of the crown and stock of one specimen, diminished less than one-half, show- 
ing, in the upper half, a section of the stock below the leaf-insertion ; in the lower left-hand 
quadrant a section of the crown, and in the other quadrant the surface of the crown. 
Fig. 5. Longitudinal section of part of a small specimen, between the bases of the leaves, of the natural 
size, showing the vascular bundles rudely collecting into plates (or wedges) on each side of the 
stock, thus giving rise to the two axes seen in fig. 8. 
Fig. 6. Another section, from the same specimen, of the natural size, taken parallel to that in fig. 5, but 
through the base of a leaf (the same as fig. 2), showing the arched form of the vascular 
: — corresponding with the arched vertex of the crown. 
Fig. 7. Longitudinal section through both leaves of another small specimen, of the natural size, in which 
the vascular stratum is very obscurely developed, though the ascending and descending 
bundles are very manifest. 
