1914] WINTON—ALFALFA AND CLOVERS 55 
Pith—This consists of comparatively large, thin-walled, pitted 
cells with no cell contents. 
Lear.—U pper epidermis ——The cells are approximately 35” 
in diameter, although often elongated, especially over the veins. 
The cell walls are strikingly sinuous and of uniform thickness. 
Numerous simple stomata are scattered over the whole surface, 
and occasional hairs, similar to those so abundant on the lower 
_ surface, occur at the base of the 
leaf. Cuticular striations are very 
distinct in cleared material. 
The palisade layer consists of 
very simple cells with breadth half 
the height. 
Mesophyll.—The ground tissue 
of this layer is made up of a loose 
mass of parenchyma with no char- 
acteristic features; accompanying 
the simple bundles, however, are 
crystal-bearing cells (fig. 3, cr) of 
diagnostic importance. The latter 
are thin-walled and arranged more 
or less end to end in longitudinal 
rows. Each cell contains a single “<5 
monoclinic crystal about 18m in Fic. 3.—Alfalfa: lower epidermis 
length, the facets of which often of leaf with unicellular hair (*), capi- 
appear corroded. tate hair (f), and stoma (s/o); cr, 
Tie lowes -cosdermis ie crystal cells accompanying bundles; 
differs from the upper principally 
in the greater number of hairs which are scattered over the whole 
surface and margin of the leaf, being especially numerous along the 
veins. The cells surrounding the hair base form a rosette. The 
hairs are of two kinds, unicellular (numerous) ard capitate (scat- 
tered). The unicellular hairs (#) are more or less sinuous, thick- 
walled, the lumen being a mere line, with small but prominent 
warts distributed over the entire length. They arise from a small, 
slightly thick-walled basal cell and average 800 w in length and 15 # 
in breadth, though the length varies up to over 1.5 mm. The 
