3^4 



An oil ca\ity occurs in the fundamental tissue at each angle of the leaf 

 and is surrounded b\" a protccti\'e circle of secretor\' cells. Stomata occur on 



both the upper and lower sur- 

 faces, the guard cells being 

 situated at the bottom of a 

 depression in the cuticle. 



The normal lea\'es, like the 

 abnoriual ones, are spirally 

 arrangetl ami occur on the 

 thickest branchlets right down 

 to the attachment with the 

 branches. They measure under 

 half an inch long, are imbricate 

 and incurved, — the physiological 

 significance of the latter feature 

 is no doubt a protection to 

 the transpiration surface, and if 

 studied in the field would pro- 

 bably be found to be spreading 

 during favourable climatic con- 

 ditions. 



A cross-section, taken above 

 the middle, shows a rhomboidal 

 figure, but below this the geo- 

 metrical shape is not so clearly 

 defined, the inner surface being 

 more embonpoint fFigure 232). 



The epidermal cells extend 

 around both surfaces, the inner 

 containing the stomata (Figure 

 236), the outer or dorsal is, 

 therefore, the assimilatory one. 

 The li\ podcrmal cells are \-ery 

 1 hick-walled and closely packed 

 ■n several rows below the dorsal 

 epidermis Figures 231 and 235), 

 bul ai-c fewer on the ventral 

 ^'d( wheic also the ])alisade 

 |iaieii(li\ina is less developed. 

 Till' fundamental tissue partakes 



Figare 233, — Transverse section throiiK'n median portion of a normal leat, 

 showing an oil cavity and the normally orientated bundle 

 below it. toRftiu-r with Ihe leaf structure in this part. 

 .4. Cttnnin^hamii, x igo. 



Ftgafe 23o. i,"f;iK«i»nl<i>rti ... i.ii>fti «fi |f.ii, ^iiMwttiM i*<('.kiiit; *ti hyi"Hlerrnal 

 "■lln IhIow the assimilatory jiurfnc'r. A. Cuniiiniihamii, 



