282 
W. O. Howarth. 
The upper (inner) epidermis also consists of long and short 
cells. The former are thin-walled, narrow at either end, but swelling 
out in the middle where their diameter is greatest. They are 
arranged in longitudinal rows and the cells of each row alternate 
with those of adjacent rows. As a result the short cells are sunk 
in depressions or troughs between the broad, protruding portions 
of the long cells. The long cells are more or less circular in 
transverse section and in the middle portion of their length from 
^ to 5 of their surface is free and exposed. The short cells may 
produce short hairs or stomata. The latter are thus to some extent 
Lower epidermis of lamina show¬ 
ing marginal pits, a, Surface view, 
X300. b, Trans, sect. X860. 
Fig. 13. Snbvar. tenuifolia. 
Trans, sect, of node of panicle. 
b, bract, p, parenchyma. X85. 
protected even when the leaf is open. The ratio of the number of 
stomata on equal areas of surface of grandiflora and tenuifolia is 
12: 11. The epidermal cells situated along the bottoms of the 
longitudinal furrows are not clearly differentiated from the rest of 
the epidermis either in size or in the thickness of their walls. 
They cannot therefore be said to form specialised structures, 
though the lamina, in folding, hinges on these cells. ' 
