116 
THE NATIONAL NURSERYMAN 
tion. Two 
tests of 
the same 
lot of 1 
western yellow pine 
seed gave 
almost identical v 
allies, 1 
though there w r as a 
difference of forty i 
days in the length of time it took one 
series to ( 
complete 
its germination 
caused by 
a pro- 
traded cold spell d 
uring the 
middle 
of the germinating 
period. ITow the 
soil moisture affects germination is 
graphically shown 
in figures 
1 and 
2 of the 1920 series 
for yellow 7 
pine and incense 
cedar 
seed. This 
data is 
further summarized in the followin 
g tables: 
Rate of Germination. 
(1920 tests) 
i 
Number 
of Days 
Required to Secure Germinations 
Soil 
Final 
Moisture 
25 
50 
75 
100 Germination 
Per cent Per cent 
Per cent 
Per cent Per cent 
Per cent 
Incense Cedar 
10.0 
31 
61 
87 
93 
8 
12.5 
28 
52 
61 
71 
16 
15.0 
23 
49 
58 
71 
34 
17.5 
28 
45 
52 
93 
40 
20.0 
26 
52 
58 
79 
28 
22.5 
22 
26 
55 
71 
24 
25.0 
44 
2 
Yellow 
Pine 
7.5 
58 
67 
87 
110 
52 
10.0 
58 
67 
87 
118 
76 
12.5 
51 
58 
68 
125 
84 
15.0 
48 
54 
62 
111 
100 
17.5 
54 
60 
79 
108 
98 
20.0 
58 
66 
78 
130 
80 
22.5 
26 
52 
93 
130 
100 
25.0 
26 
34 
72 
85 
34 
27.5 
41 
41 
58 
36 
It is quite evident from even a casual examination of 
the charts and tables that each species has an optimum 
range of soil moisture in which it germinates. Progress¬ 
ing in either direction from these values means a de¬ 
crease in total germination. In the same manner, it is 
to he noted that there is a gradual decrease in the length 
of time necessary to secure complete germination from 
the driest soils to that necessary for saturated soils. In 
5o/Z Afo/sZone /-fen CenZ 
Z/y C (Zerm/nahon ZZrCenZ fry So/Z/iZo/s/i/ne 
Confer?/ Con S/oec/es 
n/yares fo/Zorv/nj -5/oec/es nome /nc//caZe number of /cjsZs. 
the case of monterey pine this ranged from 185 days 
down to 72 days. This decrease is due to soil moisture 
almost entirely as the effect of temperature was more or 
less a constant for all tests, and is shown graphically in 
figure 3. 
With increased aridity the length of time necessary to 
secure full germination is greatly lengthened hy the lack 
of sufficient water. The seeds can absorb water slowly, 
and the few 7 that germinate straggle along, one at a time. 
With increased moisture, absorption is rapid and the 
rate of germination increases as does the total germina¬ 
tion up to the optimum. After this is reached, the rate 
increases markedly but a falling off in germination per 
cent is noted until the soil becomes so saturated that the 
lack of oxygen entirely prevents germination. That the 
lack of moisture prevented the further germination of 
the seeds in those samples containing 10 per cent water 
and less is shown by the fact that after the tests had 
been run 200 days (or more) the addition of water 
brought the total germination well up toward the op¬ 
timum. Similarly, drying out the exceedingly wet 
samples also gave an increase in germination although 
this increase was slight, not amounting to more than 3 
per cent, and occurred only in the case of the pines. 
C^C.—d/n/oc/ ?n cZays nejfo/necZ /o carr?y?Ze/e 
cyernn/no//on? o/ /ernes/ /nee seecZ Zy m o/s/isne 
con/enZ o/ so// 
The effect of the soil moisture on the total germination 
is shown in figure 4. In general, there is a fairly rapid 
rise with increasing moisture from 0 up to 15 per cent, 
a more or less flat peak, and a rather steep decline to the 
zero line again. The optimum moisture includes a range 
of from 5 to 10 per cent between 15 and 25 per cent, and 
the peak of all the species so far tried falls in this period. 
Of the eight species, only two, incense cedar and austrian 
