1914] WINTON—ALFALFA AND CLOVERS 59 
borne on a characteristic swelling of the epidermis having the 
appearance of an emergence. 
Bast.—The only noteworthy tissues are the crystal-bearing 
cells accompanying the bundles of bast fibers and the large air 
spaces, below the unicellular hairs, such as occur on the leaf. 
Phloem, xylem, and pith are similar to those of alfalfa. 
Lrear.—The upper epidermis consists of approximately isodia- 
metric cells with thin, gently wavy walls and scattered stomata. 
Hairs are absent. 
Mesophyll—The small bundles running through the simple 
parenchymatous ground tissue are accompanied by crystal-bearing 
cells, each cell containing a 
monoclinic crystal averaging 
16 w in length. 
The lower epidermal cells 
(fig. 7) have sinuous walls, 
the rather sharp bend of the 
waves being thickened and 
sometimes extended into the 
cell cavity as projections. 
Highly characteristic are the 
hornlike projections about _ : 
the stomata (sto). The walls Fic. 7. oe (Trifolium thas 
become slightly thicker and es line « remind Sa ° 
usually pitted toward the capitate hair; sfo, stoma; 160 
base of the leaf, especially 
over the veins. As on the stem, there are two forms of hairs, 
unicellular and capitate. The unicellular hairs (f) are stiff, very 
thick-walled and warty, varying in length up to 2 mm. and in 
diameter up to 30. The warts are rather more prominent than 
on the corresponding hairs of alfalfa. They arise from a conical 
Tosette of elongated cells over a large intercellular space, resembling 
in outward appearance an emergence. The capitate hairs (?), 
€ those on alfalfa, consist of a stalk formed of a few cells in a 
single row and a club-shaped multicellular head. 
ALYX.—The outer epidermis consists of simple cells with occa- 
sional wavy walls and numerous hairs both unicellular and capitate, 
