418 



are thickened ; there occur in addition small club-shaped, thin- 

 walled hairs, rich in contents, hut far fewer in number (compare 

 R. acer) (Fig. 52, B). The cells of the epidermis contain some 

 chlorophyll and have undulating radial walls, which are how- 

 ever more or less straight above the larger nerves. Only very 

 few stomata occur upon the upper surface, but upon the lower 

 surface there are, on an average, about 40 per sq. mm., either 



Fig. 52. Atiemone Richardsoni. 

 A, Transverse section of leaf. Б, The epidermis of the upper surface with a club-shaped 

 hair. C, The epidermis of the lower surface. D, Surface section of palisade-cells. E, 

 Surface section of spongy parenchyma. F, Longitudinal section through the apex of a 

 leaf; I, a lacuna between the epidermis and the epithema; .some tracheids are seen, tr. 

 (A, B, C, D, E, «''Vi; F S'Vi). 



on a level with the surface or slightly projecting; they are not 

 evenly distributed and the apertures do not lie in any fixed 

 direction. The palisade-layers constitute only a small part of 

 the mesophyll, the majority of their cells have incomplete walls 

 (Fig. 52, A). The spongy parenchyma consists of abundantly 

 branching cells and is very loose in structure. The bundles are 

 surrounded by a sheath containing chlorophyll, and the larger 

 ones have conducting-parenchyma upon their upper and lower 

 surface. 



The larger teeth of the leaf contain an epithema which 



