90 



larized layer, and is sparingly covered with large peltate hairs. The 



lateral walls are almost polygonal. An inner membrane is often 



seen to have separated from the inner walls of the cells of the 



epidermis giving an impression that we are here dealing with 



an inner mucilaginons wall (Fig. 7). But such a structure 1 



have not been able to demonstrate with any certainty. In a 



few cases I further observed that a similar structure was found 



in connection with the upper margin of the cells. It is possible 



that the spaces thereby formed contain a fluid which serves 



as a protection against the danger of 



excessive transpiration. In some cases 



I observed starch — or properly 



speaking chlorophyll grains with starch 



— in the upper epidermal cells. The 



lower epidermis is strongly papillose, 



^- -, ТУТ л J 7 each cell-cavity terminating in a pa- 



Fig. 7. Bnododendron ■' о r 



lax>ponicum. pilla. These papillae have at their 



Mbr, Membranes. L, Lumen. This gpg^ ^ CUticle which i S SÜghtlv rOUgh 



figure shews indications of the 



mucilaginous walls which occur in with prickles. The stomata are con- 



this species (Greenland). (H.E.P.) 



fined to the lower surface ot the leaf, 

 and, as is well-known from Warming's description (1. с p. 112 

 and Fig. 8 in Om Grønlands Vegetation), they all occur 

 beneath the peltate hairs with which the whole of the lower 

 surface is thickly covered. Upon the inner side of the guard- 

 cells and upon the nearest adjacent cells a cuticularized outer 

 layer may be seen. 



The palisade-cells occur in 5 to 6 layers, and are small 

 (almost about 60 /i) and diminish in height towards the interior; 

 they constitute about one-third the thickness of the leaf. The 

 spongy parenchyma consists of non-branching cells, united into 

 lamellae that stand at right angles to the longitudinal axis of 

 the leaf. Very large intercellular spaces occur between the 

 lamellae. Below the vascular bundles may be seen indications 

 of aqueous-tissue. 



