CUTICLES OF CTCADEAN EEONDS. 



165 



References : 



DiooN, Lindl. (PL 18. figs. 5-9; text-figs. 9 & 10.) 



irnemann (1856), pp. 40, 45; Taf. 12. figs. 11-14. Kraus (1866), pp. 39, 40 ; 



Taf. 22. figs. 21-23. Mahlert (1885) 



Porsch (1905), p. 11 j Taf. 1. fig. 7. 



EXAMINED 



— D. edule, Lindl. ; D. spinulosum, Dyer. 



The two species were found to be of a similar type, characteristic for the genus. In 

 B. edule the upper epidermal cells and those of the nerve-courses of the lower side of 

 the pinnae are similar, and are of two kinds — thick-walled cells elongated fairly regularly 

 in the direction of the longitudinal pinna-axis, and more or less isodiametric thin-walled 

 cells. These two kinds of cells maybe distinguished in transverse section (PL 18. fig. 7). 

 The thin-walled cells appear to be the more 

 regions between the nerve-courses are usually smaller than elsewhere. Tliey arc almost 

 isodiametric and are uniformly thick-walled. In D. spinulosum the epidermal 

 characters are similar to those in 2). edule^ though all the cell-walls seem to be slightly 



numer 



The cells of 



storaatal 



less thickened 



In both cases the lateral 



of the cells 



often slightly pitted 



(PL 18. fig. 5) (Kraus, 1866, fig. 21), and all the walls are more oi less heavily layered 



Fig. 9. 



Fig. 10. 



IHoon edule. — Lower cuticle in surface view, showing 

 six subsidiary cells surrounding a stoma-opening,5. 

 C/ the epidermal cells of tlie nerve-course (n) 

 with those of the upper surface shown in PI. 18. 



fig- 5. X 450* 



B. apimdosxim. — A stoma in median section, showing 

 the dorsal {d) and ventral (v) lignitied lamellae of 



guard 



and three intercalated series 



of cells {i^-i^) between the guard-cells »nd sub- 

 sidiary cells. {Cf. PL 18. fig. 6.) 



X 430. 



In the case of the thick- walled cells of D. edide^ihi^ lumen is often 



(PI. 18. figs. 5 & 9). 



almost fiUed up. 



Stomata occur very definitely limited to the areas between 



the nerve-courses on the 



under surface of the 



They 



much sunk in flask-shaped 



which 



In both species there are typically 



slightly deeper in B. edule than in B. spinulosum. 



three intercalated series of cells between the guard and subsidiary cells (PL 18. % 



2c 2 



