93 



epidermis. There are four kinds of hairs: — 1, unicellular hairs 

 (one kind) with a thick suberised membrane which is of impor- 

 tance only on older leaves, 2, multicellular hairs, a, long and 

 filiform, and consisting of two rows of long, narrow cells, 

 è, two kinds of glandular hairs with larger or smaller multi- 

 cellular apices upon a many- 

 celled stalk. Only the larger 

 glandular hairs occur on the 

 upper surface (I cannot help 

 thinking that Borgesen (1890) 

 in his Fig. 1 has confused the 

 two kinds of glandular hairs. 

 Fig. 1,/", shews the last stage 

 of the one kind of glandular 

 hair; i, the last stage of the 

 other; and^, shews a medium 

 stage in the development of 

 the large hairs which have 

 not been investigated in their 



younger stages). The stomata, 



, . . , , . , , Fig. 10. Ledum palustre. 



which are not protected bv 



"2, Leaf in transverse section, x. Transparent cells 

 any special kind of hairs but in the process of disorganization. Sv, Spongy 



parenchyma. 3, The tissue below the central 

 by the continuous covering vascular bundle of the leaf, y, Transparent 

 P , . f J 1 lu cells in the process of disorganization. 7, Thick- 



Of hairs, are confined to the ^^^^^^ ^^„^^^^^^ ^^^^^^ ^^ Andromeda (Green- 

 lower surface and project land: sukkertoppen). (H.E.P.) 



slightly. They are so orientated that the transverse section of 

 the leaf does not give the usual view of the stomata, which 

 may be had either in longitudinal or oblique section. This 

 orientation of these organs occurs especially in forms with fur- 

 rows ; but, as is well-known. Ledum approaches these forms 

 by the fact of its being able to roll in its leaves to some extent. 

 The inner sides of the guard-cells, as also the neighbouring 

 cells of the mesophyll, have a cuticularized outer membrane. 

 In regard to L. groenlandicum, the palisade-tissue consists 



