113 
on account of the outer walls of the epidermis being so much 
thickened. The cells of the spongy parenchyma below, and the 
inner part of the guard-cells, are suberised along the part of 
their walls which is towards the intercellular spaces. According 
to Livrorss chlorophyll grains occur both in the upper and in 
the lower epidermis. 
Fig. 26. Arctostaphylos Uva-wrsi. 
The leaf and its parts. Cf. note, p. 81. 1, x about 100; 3, 5, x about 125; 2, 4, x about 250. 
(7, 2, 4, Finmark: Bosekop; 3, Norway: Tronfjæld; 5, Iceland.) (H.E.P.) 
The palisade and the spongy parenchyma are distinctly 
differentiated, but the cells of the latter are in a great number 
of cases elongated in the same direction as that of the former, 
so that a kind of isolaterality is here found. 
The layers of palisade-cells vary in number, as do the 
individual palisade-cells in regard to height. 
In specimens from Bosekop, Tronfjeld and Sakkabani the 
XXXVI. 8 
