THE HISTOLOGY OF THE EPHEDREiE. 211 



DESCRIPTION OF PLATES. 



Plate I. 



Fig. 1. Transverse section of E. Helve ica, showing epidermal cells with thickened external wall. 

 (a) Cuticle ; (b) calcium oxalate layer ; (c) cellulose stratum, x 360. 



Fig. 2. Transverse section of E. fragilis (Algiers), (a) Division of epidermal cell into two ; (6) division 

 of one of the daughter-cells by a wall at right angles to the first division wall ; (c) cortical tannin sacs. 

 xl60. 



Fig. 3. Transverse section of E. viridis, showing large epidermal cells over ridge, one having a papilla 

 on the external wall, (a) Cuticle; (b) calcium oxalate layer ; (c) cellulose stratum. x 360. 



Fig. 4. Surface view of E. viridis, showing papillae and stomata in alternating rows. x 42. 



Fig. 5. Photomicrograph of preparation of the epidermis of E. altissima, showing position of light spots. 

 x 160. 



Fig. 6. Photomicrograph as above of E. altissima, showing image of St Andrew's cross in each light 

 spot. x 160. 



Fig. 7. Transverse section of E. nebrudensis, showing sunk stoma, guard cells, respiratory chamber, 

 ante-chamber, (a) Mucilaginous core of wall of cells forming ante-chamber. x 360. 



Fig. 8. Longitudinal section of E. distachya, showing stoma, respiratory chamber, imte-chamber. 

 (a) Mucilage core of cell wall. x 360. 



Fig. 9. Transverse section of E. nebrodensis, showing hypodermal stereoin, ami! differentiation of cortex 

 into palisade and spongy cortical cells containing starch grains and crystals of calcium oxalate. x 160. 



Plate II. 



Fig. 10. Transverse section of E. distachya, showing stereom systems well developed, (a) Welwitschia- 

 like fibres ; (b) division of epidermal cell. x 160. 



Fig. 11. Transverse section of E. distachya, showing pericyclic stereom crescent and vascular flange 

 projecting from xylem. (a) Pericyclic stereom crescent ; (b) vascular flange. x 160. 



Fig. 12. Transverse section of E. nebrodensis, showing perimedullary stereom (a). x 160. 



Fig. 13. Diagram of eight or normal bundle system, showing the entrance of the trace at a 1 , the parallel 

 course of the bundles, the behaviour of the trace at the first node (a"), the continatiou through a second 

 internode and the linking on of the traces to the bundles passing out at the third node (a 111 ). Vascular 

 crescents (a) with their component parts are diagrammatically indicated. The bud-trace (b) is indicated in 

 position below the passing out of the trace at a 1 . The splitting of the bud-trace is indicated. 



Fig. 14. Diagram of the ten or accessory bundle system. Explanation as in last. The accessory (c) is 

 indicated splitting in the region of the vascular crescent at a i , where it passes out to form an extra pair of 

 bud-traces. 



Fig. 15. Transverse section of E. trifurca, showing twelve bundles due to the presence of three leaves 

 at the node. x 42. 



Plate III. 



Fig. 16. Longitudinal section of E. nebrodensis, showing dehiscence layer. x 42. 



Fig. 17. Longitudinal section of apex of E. foliata, showing development of young internode. x 42. 



Fig. 18. Transverse section of E. fragilis, v. campylopoda, showing vascular crescents with accessory 

 splitting in between. x 42. 



Fig. 19. Diagram of junction of lateral branch with main stem, showing the bifurcation of the bud- 

 trace (b) and its course into the leaves ; the fusion of the traces of the higher leaves of the lateral branch 

 before their arrival at the first node (a), thereby making the crescent have the appearance of being made up 

 of only two bundles. 



Fig. 20. Diagram of the junction of lateral branch in the accessory system. The main features are as 

 above, while the splitting of the accessory bundle to augment the bud-supply is indicated (c) ; also the fusion 

 TKANS. ROY. SOC. EDIN., VOL. XLVI. PART II. (NO. 8). 31 



