Histological Studies in the Artemisia Formation 5 
stems. Leaf material was collected and fixed in the field. A 
modification of Flemming’s solution was used as the fixing agent. 
The material was killed from twenty-four to forty-eight hours, 
washed in the field, and preserved in 30 per cent alcohol until the 
party returned to Lincoln, when all the material, consisting of 
168 vials of leaf sections, was run up to 60 per cent alcohol, 
where it was left until it was run on up and imbedded in paraffin. 
The sections were cut a uniform thickness of 15 p, stained with 
safranin and licht griin, and mounted in balsam. Over two hun- 
dred permanent slides were made. These constitute the basis for 
the following studies and from which the figures were drawn. 
All the laboratory work was done in the laboratories of the de- 
partment of botany of the University of Nebraska. 
The methods of habitat study, or the study and determination 
of the physical factors of the formation were those laid down by 
Clements in Research Methods in Ecology. 
SOIL-STRUCTURE, WATER-CONTENT, CLIMATE 
In the southern portion of the state the Artemisia formation 
typically occupies a soil mainly of sedimentary origin, intermixed 
with loess and with a surface layer of small, slightly disintegrated 
quartzite and granite boulders. The granite of the region con- 
tains a rather high per cent of feldspar, so that on the whole the 
soil resulting from the decay of the granites is essentially a clay 
soil bearing rather fine sand particles. Farther from the foot- 
hills, however, as in the San Luis valley south of Fort Garland, 
the soil is a very fine homogeneous sand lacking the surface layer 
of small boulders. Such a soil is very deep and fine grained. It 
dries quickly on the surface, but contains too much sand ‘to bake 
hard. This fine dry surface no doubt acts as a very excellent 
mulch in conserving the moisture below. This fact taken to- 
gether with the homogeneous nature of the soil probably accounts 
for a certain peculiarity in the matter of water-content described 
below. 
In the north, especially in Estes Park, the formation occupies 
more commonly the granitic soils, since these are the most com- 
mon in that region. Disintegration of the exposed granite has 
415 
