202 ME. H. HAMSHAW THOMAS AND MISS N. BANCEOrT ON 



Fig. 5, The same. Lower cuticle, showing a section through a stoma. Note the position of the 



guard-cells, almost at the same level as the subsidiary cells. 

 Fig. 6. The same. Lower cuticle, showing a section through a hair-scar. 

 Pig. 7. Bowenia sj^ectabiliSj var. serrulata. Lower cuticle in surface vieWj showing a stoma ; the 



thickened appearance is due to the liguified lamellae o£ the guard-cells. 

 Fig. 8. The same. A stoma of the upper side of the leaf in surface view. Note the presence in this 



case of six subsidiary cells, two of w^hich are polars and four laterals. 

 Fig. 9. The same. Lower cuticle, showing a section through a stoma. Note the position of the 



guard-cells with regard to the subsidiary cells. 

 Pig. 10. Cycas revoluta. Upper cuticle in section, showing the pittings of the lateral and outer walls 



of the epidermal cells. 



Fig. 11. The same. Upper cuticle in surface view, showing the pittings of the lateral and outer walls 



of the epidermal cells. 

 Fig. 12. The same. Lower cuticle in surface view, showing the fifteen subsidiary cells surrounding a 



stoma-opening. The shading indicates the raising of the subsidiary cells beyond the general 



epidermal level [cf. fig. 13). 



Fig. 13. The same. Lower cuticle, showing a section through a stoma. Note the presence of an inter- 

 calated series of cells between the guard and subsidiary cells, and the large air-space formed 

 by the sinking of the guard-cells and the overarching of the subsidiary cells. 



Fig. 14. Cycas circinalis. Lower cuticle^ showing a section through a stoma. Note the sinking of the 



guard-cells and the absence of an intercalated series of cells [cf. figs. 5^ 9^ & 13). 



Fig. 15. The same. Upper cuticle in section, showing pitting of the outer walls of the cells. 



Plate 18. 



Fig. 1. Ceratozamia mexicana. Upper cuticle in surface view, showing thin-walled and thick-walled 



* cells. Note the layering and pitting of the thickened walls- 

 Fig. 2. The same. Lower cuticle in surface view, showing a stoma-opening surrounded by six sub- 

 sidiary cells, two of which are polars and four laterals. The cell-walls are pitted and layered 

 as in fig. 1. 



Fig. 3. The same. Upper cuticle, showing the thick- and thin-walled cells in section. 

 Fig. 4. The same. Lower cuticle : a section through a stoma, show^ing one intercalated series of cells 



between the guard-cells and subsidiary cells. 



Fig. 5. Dioon edule. Upper cuticle in surface view, showing the variation in thickness and the layering 



of the cell-walls. 



',1 



Fig. 6. The same. A section of a stoma. Note the presence of three intercalated series of cells (i'- 



between the guard-cells and the subsidiary cells ; also the dorsal and ventral liguified lamellse 

 of the guard-cells. 



Fig. 7. The same. Upper cuticle in section, showing variation in the thickness of the walls. Note 



the heavy cutin layer. 



Fig. 8. The same. A section of the lower cuticle, showing a crystal-containing space between two 



epidermal cells. The space is lined and covered by cutin. 

 Fig. 9. The same. The lower cuticle^ showing a crystal-containing space in surface view. 



Fig. 10. Encephalartos Lehmannu 



Fiff. 11. E 



showing 



g. 11. E. viUosus. Upper cuticle in surface view, showing slight pitting of the lateral wails of the 



cells and septation of an elongated cell at x. 

 Fig. 12, Zamia integrifolia. Upper cuticle in surface view, showing variation in the thickness of the 



walls and occasional pitting of the thin-walled cells. 



