160 ME. H. HAMSHAW THOMAS AND MISS N. BANCEOET ON 



The cavities of the suhsidiary cells in many cases contain crystals of calcium oxalate *. 

 The stomata are elliptical in shape, and in surface view the lignified lamellae f of the 

 ventral and dorsal walls of the guard-cells give a very characteristic thickened 

 appearance (PI. 17. fig, 1 ; text-fig. 1) to the area overlying the guard-cells. This 

 thickened area sui-rounding the pore of the stoma shows two thin patches at each pole, 



F 



owing to tlie raising up of the polar ends of the guard-cells, bringing them nearer 

 to the surface at these points, as described by Porsch for Bowenia. The projections of 

 thickening substance between each pair of thin areas strengthening the ends of the 

 stoma-ope;iing are due to the extension of the ventral lignified lamellae of the guard- 



F 



cells (see text-fig. 26, p. 176). Laterally the cntin overlying the lamellae shows fine 

 striations (PI. 17. fig. 1 ; text-fig. 1). 



Hair-scars occur on the lower surface of the pinnae, particularly on and near the 

 midrib and at the margins. They are only to be seen here and there on the upper mid- 

 rib. The scars are somewhat like a truncated cone in shape and are strongly cuticularised 

 (PL 17. figs. 2 & G). 



The cutin layer overlying the epidermal cells is fairly thick, particularly on the upper 

 surface of the pinnse. It has closely-lying striations which are seen from sections to be 

 due to folds (PL 17. fig. 3). These folds are particularly marked on the upper surface, 

 and are irregular on the lamina, but are re£:ular and run in a loniritudinal direction on 



^ ^^^ ^^^ ^^ ^ ^""b 



the midrib (text-fig. 1). They radiate from the poles of the stomata and from the bases 

 of the hair-scars (PL 17. figs. 1 & 2 ; see also references quoted). Polding of the cutin 

 is not to be found in any other genus of Cycads, and constitutes, with the undulate 

 epidermal walls, a distinguishing feature of Stangeria. 



Cycas, Linn. PL 17. figs. 10-15 ; text-figs. 2 & 3. 



References : — Bornemann (1856) 



(1866) 



figs. 1-6 ; Taf. 20. figs. 10, 11. Strasburger (1866), Taf. 41. fig. 143. Mahlert (1885), Taf. 1. 

 fig. 20. Nestler (1895), p. 343. 

 Species examined : — C. revoluta, Thunb. ; C. circinalis, Linn. ; C. undulata, Des£. ; C. MichoUtzii, 



+ 



Dyer ; C. mediae R. Br. 



The epidermal cells of C?jcas are similar on both sides of the pinnae, and are more or 

 less irregular in shape and arrangement. They are usually somewhat elongated, and are 

 three- to six-angiilar. Over the midrib the cells are more regular and rectangular in 

 shape and run parallel with the pinna-axis. In these points there is general agreement 

 with Stangeria. In C^eas, however, the lateral epiderinal walls are not undulate, 

 being at the most somewhat curved. A distinguishing feature of all species of Oycas 

 examined % is the pitting of the outer walls of the epidermal cells (PL 17. figs. 10-13, 

 fig. 15 ; text-fig. 2j. In surface view and sections, these walls are seen to be perforated 



• 



Cf. Kraus 



previous maceration. 



t Porsch (1905) ; see also Karzel (1907). 



t See also the lists giTcn by Bornemann and Kraus. 



