162 MR. H. HAMSHAW THOMAS AND MISS N. BANCEOFT ON 



intercalated cells appear to be derived from the same mother-cells as the subsidiary cells, 

 which are also from twelve to fifteen iu number. The s\ibsidiary cells are narrowly 

 and obliquely elongated (PL 17. fig. 13), so that they arch over the depression containing 

 the guard-cells in such a way as to give the appearance, in surface view, of a somewhat 

 hemispherical elevation, perforated by a small rounded opening (PL 17. fig. 12) *. Tlie 

 intercalated cells and subsidiary cells are pitted in the same way as the general epidermal 

 cells (PL 17. fig. 13). 



In the second group, the epidermal cells are irregular in form and position, as in the 

 first type ; the stomata, however, are more simple in organisation (PL 17. fig. 14). They 

 are a little sunk below the general level of the epidermis, but there is no intercalated 

 series and the subsidiary cells do not overarch the depression ; hence {he very different 

 appearance of the stomata as seen in surface view (text-fig. 2). The subsidiary cells are 

 fewer in number, though very variable, usually between five and nine (text-fig. 2) ; in 

 shape they are from isodiametric to elliptical. 



In C. circinalis and C. revoluta, fairly young stages were examined ; these showed 

 very distinctly the presence of hair-scars on the under surface of the leaves. 



The cutin layer is in all species fairly thick ; it is not characterised by any special 

 foldings or markings, as in Stangeria. 



Encephalartos, Lehra. PL 18. fisjs. 10 & 11 ; text-fii?s. 4-S. 



g„. ^^ ^ ^^ , vv^x^.- ..j^ 



KErKKENCEs:— Boruemann (1856), pp. 40, 44,; Taf. 13. figs. 1-6. Kraus (1866), pp. 33, 34; 



Taf. 20. figs. 12-15 ; Taf. 21. fig. 16. Mahlert (1885), Taf. 1 . fig. 23. Nestler (1895), pp. 346- 



348 ; Taf. 11. figs. 5-8 ; Taf. 12. fig. 9. 

 Species examined : 



Woodii (? hort.) ; E. horridus, Lelim, ; E. caffer, Miq 



Wildea 



) 



Heviewing the species examined as a whole, there seems to be a considerable amount 

 of variation in the form of the epidermal cells, even in the cells of the same pinna (text- 

 fig. 5). Generally speaking, the cells are somewhat elongated and the longitudinal axes 

 run in the direction of the longitudinal axis of the pinna (PL 18. fig. 11 ; text-fig. 4). 

 The transverse walls are usually obliquely placed with regard to tlie pinna-axis ; the 

 cells are three- or four-angular and rhombic in shape. 



In E, Lehmanni (text-fig. 5), B. caffer, and E. Immginosiis, where the cells are small 

 and more nearly isodiametric, their greater diameter is usually transversely or obliquely 

 placed with regard to the axis of the pinnae ; in B. horridus the cells are irregular in form 

 and direction, particularly in the region of the lobe-bases. 



The epidermal cells of the lower surface are of two kinds— those of the nerve-courses 

 and those of the stomatal areas. The cells of the nerve-courses are similar in form to 

 those of the upper surface. They are usually somewhat narrow and elongated and are 

 arranged in longitudinal lines. The cells of the stomatal areas are typically shorter, 

 broader, and more isodiametric. 



♦ Cf. Boriiemann (1856), Taf. U. fig. 4. 



