IMPORTANT RANGE PLANTS. 61 
APPENDIX: PLAN OF STUDY. 
In obtaining information on the individual forage species, consid- 
eration was given as far as possible to the following points: 
1. Name of plant, both Latin and common. 
2. Distribution. 
a. Characteristic zone. 
b. Most typical habitat; abundance and density of stand. 
3. Usual plant associations and communities. 
4. Habit of growth. 
a. Annual or perennial. 
b. Tufted growth, height growth, and character of herbage. 
5. Character of root system. 
a. Spreading fibrous root, or taproot with lateral rhizomes. 
h. Depth of roots in soil. 
6. Ecological requirements. 
a. Soil and moisture preferences. 
b. Drought resistance. 
7. How flower stalks are sent up. 
8. How fertilized. 
9. When seeds are matured. 
10. How and when seeds are disseminated. 
11. Seed habits, strong or weak. Viability tests. 
12. Period of germination. 
13. Classes of stock which graze it. 
14. Suitability for early or late grazing. 
15. Palatability when green and when matured. 
16. Time at which it is usually grazed. 
17. Relative forage value. 
Information on the points in the above outline was secured through 
investigation extending over four successive years. The actual eco- 
logical requirements of the various species could be determined only 
through physical-factor measurements. 
An important factor affecting the distribution, and more particu- 
larly the succession of vegetation, is available soil moisture. Experi- 
ments showed that the greatest physiological activity is manifested 
at the time fertilization is taking place or immediately after the 
completion of the flower-stalk production but prior to a pronounced 
development of the seed. 
The comparative ability of the various species to withstand 
drought was determined by ascertaining for each species the amount 
of moisture remaining in the soil when the plant had wilted to a 
point from which it could not recover. Unless pronounced wilting 
was actually in progress as a result of aerial and soil conditions, it 
was necessary to bring it about by cutting off the water supply from 
the plant. In making determinations in the field one of the methods 
used was as follows: The plants to be tested were dug up, with the 
roots undisturbed in their own soil, particular care being taken to 
prune off as little of the root system as possible. The block of soil 
