440 BOTANICAL GAZETTE [DECEMBER 
developed in the margins of the leaves. The mestome strands show 
the same structure in regard to the leptome and hadrome as observed 
in theculm; there is also the same variation from oval to orbicular 
(in cross-section), and the mestome sheath is typically developed with 
the inner cell wall heavily thickened. Outside the mestome sheath 
the ordinary thin-walled parenchyma sheath is found mostly contain- 
ing some chlorophyll. I have not observed a single instance in these 
alpine species where mestome strands occurred beneath the bulli- 
form cells; but in Deschampsia caespitosa from Graymont, at a 
much lower elevation, some few very fine veins were observed between 
the larger ones,-thus being located directly underneath the bulliform 
cells. It might be mentioned at the same time that Duvat-JOuvE 
(J. ¢., pl. 16, fig. 5) figures a leaf of a French specimen in which 
a very small mestome strand occurs between each of the two larger 
veins, just beneath the bulliform cells, 
The chlorenchyma is very compact in these alpine species, and is 
mostly developed as a palisade tissue. In Poa Lettermanni, however, 
it is developed as palisades only around the mestome strands, radiat- 
ing toward their center, while in the other portions of the leaf this 
tissue consists of much shorter and roundish cells (figs. 7,8). In Poa 
flexuosa there are no palisades at all ; in Phleum the cells are hardly 
high enough to be called palisades, even if some distinction may be 
noticed between the ventral and dorsal portion of the chlorenchyma. 
In all the other species the chlorenchyma constitutes a homogeneous 
palisade tissue, vertical to the surface or radiating toward the center 
of the mestome bundles. It is a very compact tissue throughout the 
leaf blade, and rich in chlorophyll. 
The leaves of the alpine Gramineae are mostly erect, though oe 
exactly vertical, and are frequently conduplicate or with the margins 
involute; they are seldom spreading or perfectly flat. In this way they 
agree to some extent with the species from the plains, although the 
internal structure is very different, at least in certain genera. In the 
alpine species the leaves are often furrowed on the ventral face, but 
not to the extent so commonly observed in the lowland species, 10 
those that inhabit the plains for instance. This may perhaps be the 
reason why the stomata in the alpine species are so much deepet than 
in those from the lowlands, where they are level with the epidermis, but 
