1 66 Corky Excrescences on Stems of Zanthoxylum, 
Araliaceae. 
Aralia spinosa. Kevv Museum: cork formed under a series of 
thorns; no special cones. 
Cacteae. The thorns are imbedded, at their base, in a resistent 
tissue formed by a cork-cambium (Delbrouck) : see figure of 
Echinopsis oxygona in D.’s paper, ‘ Die Pflanzenstacheln also 
Goebel in Schenk’s Handbuch der Botanik, iii (i), p. 271. 
Euphorbiaeeae. 
Euphorbia laclea. Kew Museum : for description see above, p. 160. 
E. splendens. For Mittmann’s description see above, p. 161. 
EXPLANATION OF THE FIGURES IN PLATES 
VII AND VIII. 
Illustrating Mr. Barber’s Paper on Corky Excrescences on Stems of Zanthoxylum. 
Figs. 1 and 2. Specimens of Zanthoxylum Clava-Herculis ; (i) from Kew 
Museum, (ii) Cambridge Botanical Museum, — from photographs. 
Fig. 3. Old thorns of Zanthoxylum alatum. Fig. 4. Young shoot of Z. alatum. 
Fig. 5. Transverse section through the apex, showing the arrangement of the 
young leaves. The faint lines represent the vascular system. 
Fig. 6. Transverse section through a young leaf-base, showing the first appear- 
ance of the gland at the base of the thorn. 
Fig. 7. The first appearance of the young thorn and vascular bundle. 
Fig. 7 a. The gland at its base, more highly magnified. 
Fig. 8. Young thorn, longitudinal section. 
Fig. 9. Elongated pitted cells of a young thorn. 
Fig. 10. An isolated pitted cell from a large green thorn. 
Fig. 11. Longitudinal section through the base of the thorn in autumn, showing 
the formation of the secondary meristem, from a photograph. 
Fig. 12. Small portion of a longitudinal section through the point of junction of 
a thorn and its corky base. The cells on the two sides of the split differ in size 
and character. The larger cells are derived from the primary meristem at the 
base of the thorn, while the smaller brick-shaped cells are the first products of the 
secondary meristem which gives rise to the corky cushion below the thorn. 
Fig. 13. Caesalpinia Nuga , from a drawing belonging to Mr. W. Gardiner. 
Fig. 14. Z. carolinianum , from a photograph of a specimen in Kew Museum. 
Fig. 15. ‘Stems’ in Kew Museum, brought from Khasia by Sir J. D. Hooker, 
from photographs : a. Zanthoxylum , probably Z. hamiltonianum. b. Mezoneurum 
cucullatum. c. Toddalia aculeata. 
