1908] HOLM—ALPINE GRAMINEAE 439 
storage tissue surrounding the veins. The distribution of the stereome 
is mainly the same in all the species and rather scantily represented 
as compared with the culm. The mestome strands are constantly 
arranged in a single plane and are very uniform in structure. 
In the epidermis the outer cell wall is generally quite thick on the 
dorsal face, but less so on the ventral; the cuticle is smooth, and very 
distinct in all the species. The characteristic bulliform cells between 
the mestome strands on the upper face of the blade were observed in all 
the species, but they are not very large, and are sometimes confined 
to a single group, one on each side of the midrib, as in Poa Letter- 
manni, P. flexuosa, P. gracillima, and P. rupicola; in the other species 
there may be four to six or even a larger number of groups in the lateral 
parts of the leaf blade. In Poa Lettermanni (figs. 7, 8) the leaves 
are glabrous on both faces, but in the other species they are generally 
a little scabrous from small, obtuse papillae. Pointed, prickle-like 
projections occur in Festuca, Agrostis, Poa rupicola, P. Fendleriana, 
and P. alpina from Long’s Peak. Hairs are not frequent, but were 
observed on the ventral face of the blade in Poa gracillima, Calama- 
grostis, and Avena, and on both faces in Trisetum and Agropyrum 
Scribneri. With the exception of Trisetum subspicatum, which may 
be called densely hairy, the hairs in the other Gramineae are so scat- 
tered that they are often hardly visible to the naked eye. 
The stomata (fig. 7) occur mostly on both faces of the blade, but 
as a rule are most frequent on the ventral face; in some species of 
Poa, Agropyrum Scribneri, Calamagrostis, and Trisetum they are 
confined to the ventral face. They are usually sunk, and sometimes 
covered by papillae or hairs, and they occur especially on the sides 
of the furrows between the mestome bundles. Their position in 
reference to the surface may sometimes vary on the same leaf; for 
instance, in Agropyrum violaceum they are free on the ventral face, 
but sunk on the dorsal, while the opposite is true of Avena ; in Des- 
champsia caespitosa they are level with the epidermis, and not covered 
by the papillae. Otherwise the structure of the epidermis offers no 
Points of particular interest. 
The stereome is poorly represented in most of these species, and 
occurs often only as a very small hypodermal strand outside the larger 
mestome bundles (fig. 8) and not in contact with them; it is better 
