16 Raymond John Pool 
Scutellaria brittom. Plate III, fig. 18. 
This material came from a holard of 9.4 per cent. A very 
thick cuticle (8 ») covers both surfaces with a smooth shiny coat. 
The epidermal cells are filled with a mucilaginous sap. The 
chlorenchyma is composed of two rows of prolate palisade cells 
and from three to four rows of more or less globose sponge celis.. 
The whole tissue is very compact, the intercellular air spaces be- 
ing reduced to mere lines or tiny triangular openings. No water 
storage cells are found except a sheath of a single row of clear 
cells about the vascular bundles. The shade form of the species 
shows a much looser leaf structure, but the above is the normal 
for the Artemisia formation. 
Thelypodium wrightu, Plate III, fig. 19. 
Scattered, forked epidermal hairs occur here with a well-de- 
veloped cuticle over both surfaces. The epidermal cells are large 
and lens-shaped. The chlorenchyma is much like that of Scutel- 
laria above except that there are a greater number of rows of 
cells. In this species there are four regular rows of closely ag- 
gregated palisade cells and four to five rows of compact globose 
sponge cells. The only storage tissue present is found in the vas- 
cular bundle sheath of a single cylinder of cells. 
Pentstemon trichander. Plate III, figs. 20 and 21. 
Figure 20 shows the structure of the stem leaf and figure 21 
that of the rosette leaf from the same individual of this species. 
The holard at 2 dem. was 8.5 per cent; the temperature on the 
surface of the soil was 50° C.; the humidity was 23 per cent. 
At a height of % m. or that of the stem leaf the temperature was 
35° C. and the humidity was 32 per cent. Both the leaves are 
well-cuticularized, the cuticle being from 4 to 6 » in thickness. 
The chlorenchyma in the stem leaf is entirely composed of pali- 
sade cells, seven rows in number. In the rosette leaf there are 
the same number of rows of cells, but the four lower rows are 
very sponge-like, with comparatively large intercellular air spaces. 
The three upper rows are like those in the stem leaf. In the 
rosette leaf the epidermal cells are filled with a dark mucilag- 
inous cell sap. The stem leaf shows less color in the epidermal 
cells, 
426 
