CUTICLES OF CYCADEAN FRONDS. 



171 



and narrow, 

 iDetween the 



stil] 



running quite straightly, and having 



pointed ends. The 



shorter and broader and more irregular, but they are 



ghtly elongated, except in the immediate neighbourhood of the stomata 



In 



stomatal areas the cell-walls 



sometimes thinner than they are on the upper 



surface : this is best seen in Z. Skinneri and Z. Lindeni 



I 



Z. Fischer i the upp 



epidermal cells and those of the nerve-courses and stomatal areas are of about the same 



thickness. 



Pittings are sometimes plainly seen (PI. 18. fig. 12), particularly in the case of the 

 thin-walled cells of nerve-courses. Occasionally the cellulose of the epidermal cells 

 is layered ; and in some cases very much elongated cells are septate as in Z. Ottonis 

 and Z. Skinneri. 



Fig. 19. 



Fig. 20. 



Zamia FiscJieri. — Upper cuticle in surface view. 



x450. 



Z. 



nneri 



Upper cuticle in surface view. Cf. 



amount of variation in the thickness of the cell- 

 walls with that shown in text-fig. 19. x450. 



Stomata occur on the lower sides of the leaves 

 courses ; they are sunk only slightly below the 



definite 



between the 



of the epidermis, there beiu 



ntercalated series of cells between the oruard-cells and subsidiary cells (PI 



fig. 13) 



The lignified lamellae 



of the <»uard-cells may be seen, as in Stangeria (and Bowenia) 



characterist 



lightly below the level of the subsidiary cells 



The subsidiary cells 



number and arrangement ; there are from four to six, consisting of 



elongated cell at each pole of the stoma, and two (sometimes 



lateral 



cells at each side (text-fig. 22) 

 (text-fig. 21). 



Sometimes a second series of lateral cells is present 



SECOND SERIES. — BOTANY, VOL. VITI. 



2 



