Rag Ss 
Histological Studies in the Artemisia Formation 13 
in this direction by developing a much thicker cuticle and more 
water storage tissue than is to be found in its lanate relatives. 
The upper cuticle is 6 » thick, while that on the lower side 1s 
scarcely less. The chlorenchyma is composed of two rows of pal- 
isade on the upper and lower sides, separated by a broad band of 
storage tissue composed of large, clear, globose cells. Numerous 
resin canals are scattered through the storage layer, the signifi- 
cance of which can not be explained at present. This species may 
be classed with the smooth-leaved, more or less succulent 
xerophytes. 
Alliomia linearis. Plate II, fig. ro. 
Material of this species was collected in the same situation from 
which the Artemisia material for figures 1 and 2 was taken, where 
the holard was from 8.0 to 10.0 per cent in fine sandy soil.. In gen- 
eral the structure is about the same as E. S. Clements found in the 
same species from a gravel slide with a chresard of 2.5 per cent 
to 5.5 per cent. However, the leaf is somewhat more xerophytic 
in structure than the leaf found by Dr. Clements. A rather strik- 
ing point noted was in the cuticularization of the leaf. The lower 
- cuticle is thicker than the upper cuticle, an apparent anomaly 
which is probably explained by the fact that during the hot hours 
of the day,the leaf is folded closely on the midrib with the lower 
epidermis outermost. The shape is that of an acute dihedral angle 
with the midrib at the vertex. , 
There are five rows of prolate palisade cells with no indication 
of sponge cells'in the lower portion of the leaf such as Clements 
found in her material. We have here a typical staurophyll. The 
vascular bundles are small and are always encased by a sheath of 
storage cells. There are many crystal sacs scattered through the 
chlorenchyma. 
Odostemon aquifolium. Plate II, fig. 11. ~ 
This species is not a true associate of the Artemisia, but is found 
in the formation where it meets a forest or a thicket formation. 
It is to be regarded as an invader. The leaf is interesting because 
of its extreme xerophytic structure. The cuticle on the upper - 
surface is made up of a series of undulating layers or lamellae and 
423 
