62 
BULLETIN 791, U. S. DEPARTMENT OF AGRICULTURE. 
tion lias manifested itself, however, the less hardy palatable plants 
have been killed. In such serious instances of physiological weak- 
ness, the aerial development of the remaining vegetation is often 
well-nigh lacking ; yet the buds at the crowns of the plants, as well 
as a considerable portion of the root systems, may survive. So long 
as the factor disturbing the physiological balance of the vegetation 
persists, most of the. buds at the plant's crown remain dormant, only 
an occasional aerial shoot being produced to elaborate food and 
nourish the plant. Where a considerable portion of the vegetation 
is alive,, yearlong protection, or grazing after seed maturity, will 
greatly promote revegetation. In figure 26 is indicated the effect of 
protecting yearlong a moderately depleted range. The unprotected 
area represented has been grazed moderately by sheep and cattle 
before seed maturity each year during the period of the test, and 
corresponds to the grazing practice in vogue prior to the experiment. 
When the protected areas shown in the figure were fenced in 1913, 
the vegetation appeared identical with that outside in character, 
density, and vigor. 1 The difference in 1917 in these particulars is 
summarized in Table 7. 
Table 7. — Comparative height and density of vegetation on plot protected from 
grazing for fire successive years and on unprotected adjacent range grazed 
annually l)y sheep, usually well in advance of seed maturity. 1 
Density per square foot. 
Relative height (physiological 
index). 
Plant. 
On pro- 
te?ted 
plot. 
On open 
range. 
Per cent 
differ- 
ence. 
On pro- 
tected 
plot. 
On open 
range. 
Per cent 
differ- 
ence. 
45.6 
1.6 
28.2 
1.4 
.7 
38 
12 
1.47 
3.06 
0.85 
1.20 
42 
Slender wheat grass (Agropyron tenerum) . 
61 
3.2 
45.6 
.8 
3.2 
100 
63 
2 75 
34 
1-20 
1.90 
5.20 
1.70 
16.9 
1.4 
2.1 
5.6 
12.7 
1.4 
4.9 
4.2 
3.5 
0.8 
2.8 
1.4 
1.03 
4.40 
1.20 
46 
Tall larkspur {Delphinium barbeyi) 
Low pea vine (Lathyrus leucanthus) 
15 
29 
1.20 
.8 
4.8 
12.0 
7.2 
4.0 
2.4 
4.0 
2 75 
32 
65 
51 
80 
2 17 
65 
2. 82 
2.56 
2.13 
1.18 
24 
Small mountain porcupine grass (Stipa 
54 
2.92 
1.95 
2.92 
0.96 

Spiked trisetum ( Trisetum spicatum) 
Tongue-leaved violet ( Viola linguacfolia)... 
51 
1 The figures here given were compiled from a bisect 16 feet long and 1 inch wide and outside of (he pro- 
tection plot. Owing to the unwieldiness of such a sketch, only half of its length is shown in figure 26. 
2 Indicates more individuals per square foot on the unprotected range than on the protected range. 
In the density of the vegetation per square foot, the difference in 
the percentage figures for the highly palatable perennial plants is 
1 Oomparativp average height growth of the different spocios on the fenced and un- 
fenced areas is here used as an index of physiological vigor, of which it is believed to be 
a reliable criterion. 
