CUTICLES OF CTCADEAN FEONDS 



173 



the nerve-courses, even on the upper surface of the leaf 



As is usual, on the lower 



of 



surface, the cells between the nerve-courses are shorter and broader. No pittin 

 the walls was observed. 



Stomata occur in both the upper and the lower epidermis (PL 17. figs. 7 & 8). 

 e few and scattered on the upper side, occurring principally in the middle of the 1 



They 



half of the pinnae, between the 



they decrease in number towards the upper half 



In all cases their long 

 The cruard-cells are situated 



and margins. They are fairly abundant on the lower side 



axis is approximately parallel with that of the pinnae. 



practically at the level of the epidermis (PL 17. fig. 9), there being no intercalated 



series of cells between them [and the subsidiary cells— they are less sunk than those 



of anv other genus except Stangeria [cf. PI. 17. fig. 9, Bowenia, with fig. 5, StmigeHa ; 



Fig. 25. 



Fig. 24 



Bowenia sj)ectabilis var. serruTata. — Upper cuticle 



in section, x 450. 



vhta. — Upper cuticle 



in surface view. X 450. 



fig. 14, Cycas circinalis ; and PL 18. fig. 13, Zamia integrifolia, for degrees of sinking 



of suard-cells without an intercalated series of cell 



The stomata are surrounded by 



from four to six subsidiary cells, the walls of which are fairly thin CPl. 17. figs. 7 & 8), 

 particularly in the case of the stomata of the upper leaf-surface. On account of the 



level of the epidermal cells, 

 plainly seen, giving a characteristi 



position of the guard-cells, i.e. 

 the lisjnified lamellae of dorsal and 



almost at the general 



wall 



s 



appearance in surface 



(PI. 17. figs. 7 & 8 ; cf. Stang 



fig.l) 



As previously 



described by Porsch in the case of B. spectahilis *, the raising-up of the polar ends of the 

 guard-cells is indicated in surface view by the presence, at each pole of the stoma, of two 



• Porsch (1905), p. 13 ; Taf. 1. figs. 1 & 3. See also Nestler (1895), Taf. 13. figs. 19 & 20, h 



2d2 



