aes 
Fig. 2. Longitudinal section of ditto, taken through a yascular bundle: a, epidermal cells; 6, pulpy 
48 DR. J. D. HOOKER ON WELWITSCHIA. 
Fig. 13. Transverse section of a root-fibre, showing the periderm, parenchyma, vascular bundles, and 
scattered sclerogen-cells, Magnified 60 diams. 
Fig. 14. Liber-cells, &c., from the same. 
Fig. 15. Pitted vessels from the root. 
(All the above, except figs. 6 & 7, are more or less magnified.) 
Piate XIV. Leaf-tissues (p. 18). 
Fig. 1. Transverse section of a portion of a leaf, magnified 40 diams.: a, epidermal cells; 4, lax pulpy 
cellular tissue, into which the stomata open; ¢, bundles of liber-cells; d, spicular sclerogen- 
cells; e, parenchyma of leaf. 
tissue; ¢, liber-bundles; d, sclerogen-cells ; e, parenchyma of leaf; J; vascular bundle. 
Fig. 3. Vascular bundle in longitudinal section: 4, bounding cells with thick and pitted walls; 4, liber- 
bundles; c, cambium-layer ; d, pitted and slit-marked vessels; e, closed spirals and open 
spirals. 
Fig. 4. Tissue from beneath epidermis of old leaf after boiling in caustic potash, consisting of masses of 
sclerogen-cells in pulpy cellular tissue and liber-cells. a 
Fig. 5. Epidermis of upper surface of leaf and opening of stomata. Magnified 240 diams. | 
Fig. 6. The same, of lower surface of leaf. 
Figs. 7 & 8. Sections through stomate, taken parallel to the guard-cells. Magnified 240 diams. 
Fig. 9. Section through axis of guard-cells. 
Fig. 10. Section through stomate, through the ends of the guard-cells. 
Fig. 11. The same, through the middle of the guard-cells. 
Fig. 12. The same, through the confluent extremities of the guard-cells. 
Fig. 13. Portion of cuticle surrounding a stomate. . : 
(Figs. 5-13 are all magnified 240 diams.) 
Fig. 14. Vessels from an old root, showing how their cavities become filled with secondary deposits. 
Fig. 15. Vessels from old vascular stratum in the stock, showing the pits of the vessels united by a 
delicate spiral line. 
