372 



as ill oilier species of JuuiuhchIks tlie outer, lateral walls ot 

 the iruard-cells in transverse section are convergent inwards 

 |Fig. 22, B\. In the lobes the stomata are arranged more or 

 less parallel with the main bundle, otherwise they are without 

 any fixed order. According to my computation about the same 

 number of stomata occur per sq. mm. upon both surfaces of 

 Ihe leaf, viz. about 70. ïh. Resvoll found 67 per sq. mm. 

 upon the upper and 83 per sq. mm. upon the lower surface. 

 Th. Resvoll records 2 — 3 palisade-layers. The leaves I in- 

 vestigated had two layers which taken collectively constituted 

 1/2— 1 3 of the thickness of the mesophyll. The individual 

 cells of the palisade-layers are usually barrel-shaped ; the 

 uppermost layer is often higher than the lower ones, and in 

 some places the palisade may be said to occur in but one 

 layer, the cells of which are then more strongly differentiated as 

 palisade-cells. The palisade-cells are slightly inclined towards the 

 leaf-apex. Usually there is a rather distinct passage from the 

 palisade to the spongy parenchyma; the latter is very lacunose 

 in structure and is composed of branched, often somewhat 

 stellate cells (Fig. 22, F\. Long slit-like lacunae often occur 

 within the subepidermal layer upon the lower surface. 



Along the main bundles of the leaf, upon both the upper 

 and lower surface, run elongated elements which in transverse 

 section are circular, close-set, and non-prosenchymatous; they 

 touch the epidermis of both surfaces ; along the somewhat 

 weaker bundles such cells occur only upon the lower surface, 

 while the palisade-layers upon the upper surface are not invaded; 

 the smaller bundles are surrounded only by a sheath containing 

 chlorophyll (Fig. 22, A). Here as in other species, each lobe 

 terminates in a hydathode in which the mesophyll is trans- 

 formed into an e pi the ma the intercellular spaces of wliich 

 open out in water-pores, in exactly the same manner as in 

 R. nivalis (see Fig. 27, Ai. 



The dwarf-plant from King Charles Land (Fig. 18) had leaves 



