Dec. if>, 1925 Studies in Western Yellow Pine Nursery Practice 1105 
Table I. — Germination percentage under different depths of cover , 1912 
Comparison of nurseries 
Depth of cover 
Savanac 
Priest 
River 
Boulder 
Average 
yi inch_ __ _ 
Per cent 
50.6 
48.6 
Per cent 
41.4 
40.8 
Per cent 
31.8 
27.2 
Per cent 
41.0 
38.9 
inch___ 
The differences in these figures for the different nurseries may be 
partly explained by the fact that sowing was done May 1 at Savenae, 
May 15 at Priest River, and June 5 at Boulder, because of differences 
in the beginning of the growing season and the time when it was 
possible to do the sowing. Climatic differences at the three places 
are indicated in Table II. 
Table II. — Comparison of temperatures and precipitation at nurseries , 1912 
Nursery 
Monthly mean 
temperature 
Mean maximum 
temperature 
Precipitation 
May 
June 
May 
June 
May 
June 
Priest River____ ... 
° F. 
51.7 
50.6 
46.2 
o F 
60.5 
59.0 
57.4 
° F. 
80 
83 
75 
O J? 
97 
97 
90 
Inches 
2.68 
2.33 
4.03 
Inches 
2.14 
1.12 
1.32 
Savenac___ __ 
Boulder.____ ___ 
The temperature figures furnish one evident reason why germina¬ 
tion at Boulder was lowest. The higher mean maximum air tem¬ 
perature at Savenac was probably one of the contributing factors 
in producing greatest germination at that place, when combined with 
the advantage of early sowing. 
While the differences between germination at the two depths are 
quite small, the fact that they are consistently in favor of the shal¬ 
lower depth of 34 inch at all three places and under different condi¬ 
tions is excellent evidence, when taken in connection with similar 
evidence from later experiments, to show that 34 inch is a better 
depth than % inch for covering yellow pine seed. 
The germination figures obtained in the 1913 study at Priest River 
are shown graphically in Figures 1 and 2, where the effects of the 
different depths of cover and of the two methods of sowing are com¬ 
pared. 
The following points in regard to germination are brought out by 
these curves: 
(1) Greatest germination was attained with a 34-inch depth of 
cover, which was the shallowest; and the second greatest was with 
inch depth. The 34-inch and %-inch covers showed about the 
same amount, due to the fact that on the %-inch broadcast plot the 
depth of cover was reduced by washing, with a consequent marked 
increase in germination for that plot. The deeper sowings showed 
still less, the %-inch plot taking fifth place, and the 1-inch plot sixtli 
place. 
