126 
alpina; it is deciduous, hairs are absent, and there is only a 
waxy covering. 
The upper and lower epidermis are only slightly thickened 
and have no specially cuticularized layer beneath the cuticle; 
the lateral walls are slightly undulating. The stomata are con- 
fined to the lower surface and do not project. 
The palisade-tissue consists of 1—2 layers of cells, with 
a height of as much as 100 y, and it is somewhat unequally 
developed , the lower 
layer being less deve- 
loped when the upper 
consists of long cells. 
The cells of the spongy 
Ba, ay Ol 
is 
7 
parenchyma are more 
elongated in the vertical 
than in the horizontal 
direction and often 
branch but slightly; the 
intercellular spaces are 
large. The whole of the 
mesophyll is loosely 
or. 
ae 
# 
built. In the material at 
my disposal I have not 
observed any difference 
between Danish, Sub- 
arctic, and Arctic spe- 
Fig. 37. Vaccinium uliginosum. cimens. 
Transverse section of stem >< 180. (Phot.) The stem. The 
primary cortex consists, 
according to SEGERSTEDT, "of a few layers of cells of which 
the outermost have scanty chlorophyll-contents with walls 
thicker than those of the inner, which are loosely con- 
nected and the contents of which are colourless.” The epidermis 
