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, 
b, 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 BôrGesex (1890) 
in his Fig. 1 has confused the 
two kinds of glandular hairs. 
Fig. 1, f, shews the last stage 
of the one kind of glandular 
hair; 7, the last stage of the 
other; and g, shews a medium 
stage in the development of i 
the large hairs which have 
not been investigated in their 
younger stages). The stomata, é 
Fig. 10. Ledum palustre. 
1, Leaf in transverse section. z, Transparent cells 
any special kind of hairs but in the process of disorganization. Sv, Spongy 
R Eg parenchyma. 2, The tissue below the central 
by the continuous covering vascular bundle of the leaf. 7, Transparent 
: cells in the process of disorganization. 7, Thick- 
of hairs, are confined to the walled cells like those in Andromeda (Green- 
lower surface and project land: Sukkertoppen). (H.E. P.) 
slightly. They are so orientated that the transverse section of 
which are not protected by 
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, ZLedum approaches these forms 
by the fact ef 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 
