NortuH Haven Sanp PLains 587 
The lower epidermis is made up of smaller colorless cells. The 
cells are much enlarged locally around the bases of long, simple 
unicellular hairs ; subepidermal strands of stereome occur on the 
upper surface as follows: On the outside of the water-holding 
tissue over the keel and above eight of the largest mestome 
bundles. Similar strands are found on the under surface at the 
keel and below a part of the mestome bundles including the larger 
and some of the smaller ones. The small mestome bundles are 
each enclosed by a parenchyma sheath showing four or five cells 
in cross-section. Stomata occur on both surfaces, but are far 
more abundant on the lower surface. 
PANICUM DEPAUPERATUM. — Upper side of leaf deeply grooved 
between the bundles, with shallow grooves opposite on lower side ; 
also shallow grooves opposite the mestome bundles on the lower 
surface. Keel is not prominent and its bundle is only slightly 
larger than the other largest mestome bundles. Bundles are en- 
closed in a sheath of stereome which is not fully developed in 
some of the smaller ones, the cells having lamellated and pitted 
walls. Outside of the stereome sheath is a parenchyma sheath 
found in connection with all the bundles. The parenchyma- 
sheath cells are of good size and show no green coloring matter. 
Two or more cells of the stereome sheath are replaced on the 
upper side by parenchyma-cells, a tier of which extends from the 
_ bundle upward to the subepidermal stereome strand of the ridge 
of the upper surface. Similar tissue connects the bundle with the 
subepidermal stereome tissue of the lower surface. A layer of 
rather thick-walled cells (probably tracheids) separates the hadrome 
from the leptome in the larger mestome bundles, but in the smaller 
ones the elements are not clearly differentiated. Subepidermal 
strands of stereome occur in the leaf-margins and above and below 
each bundle. The epidermal layer of the upper surface consists of 
colorless cells, very small over the stereome strands, with large 
cells in the grooves that probably function as bulliform cells. In- 
ferior epidermal cells are colorless, of medium size between the 
mestome bundles, but very small over the stereome tissue oppo- 
site the bundles. Certain epidermal cells of the ridges of the 
upper surface are extended into stout, blunt-pointed hairs, and 
Sharp-pointed unicellular hairs are borne in the grooves of both 
