3H(5 



(Fijî. 32, /y, T). The stomat.i are cillicr on a level willi tlie 

 surface or jtroject sli<rlitly. IJokgeskn and Wagnkk record Ihe 

 number lo be e(iual u|)Ou both surfaces, IIesvoll records 44 

 per sq. mm. upon the u[)per as against 62 per sq. mm. upon the 

 lower surface. Chlorophyll is present in the epidermis. From 

 one to two layers of pa li s ad e-cells occur which are scarcely 

 twice as liiiih as tiiey are broad and are somewhat barrel-shaped ; 



Fig. 32. R. pygmœus. 



A, Transverse section of leaf (Danmarks Ö; "*/i). B, Epidermis of the upper surface of 

 the leaf (ibid; ""/i)- C, Epidermis of the lower surface of the leaf (ibid; ""/i). D, Sur- 

 face section of palisade-layers (ibid.; ""/i). E, Surface section of spongy parenchyma 

 (ibid.; ""/i). F, Transverse section of leaf-stalk (22/1). 



they constitute from ^h to ^U of the thickness of the mesophyll. 

 The spongy parenchyma consists of branched cells and is 

 very loose in structure especially in its lower part where large 

 slit-like lacunae are often seen between the subepidermal layer 

 and the rest of the mesophyll; (Fig. 32, A,D,E). The bundles 

 are not accompanied by stereom and are surrounded by a sheath 

 containing chlorophyll. 



Each leaf-apex terminates in an e pith em a the structure 



