NATURAL REGENERATION OF DOUGLAS FIR. Le 
eo 
| forest renewal when the forest is removed by fire or cutting. (PI. 
@ Lio) 1) 
The unintentional influence of man as a distributing agent on the 
| large burns or barren areas is negligible. 
Gravity assists distribution in mountainous or hilly regions. 
GERMINATION AND SEEDLING DEVELOPMENT. 
The factors necessary for germination are aeration, moisture, and 
favorable temperature. 
| Aeration is essential for plant growth, and the lack of it causes 
_ poor growth or death in growing plants and dormancy in seeds. 
| Even though conditions may, be favorable for the germination of 
| seeds, a lack of oxygen resulting from inadequate aeration will keep 
| them dormant. The seed that is buried out of reach of the air or is 
| in moist duff where the oxygen supply is small may remain dormant 
_ for long periods. Moisture is necessary to start germination, but too 
| much moisture may cause the death of the young sprout by the exelu- 
sion of oxygen. 
Although the seed may have sufficient moisture and oxygen for 
germination, it will remain dormant if it is kept cool. This is often 
the chief factor in keeping the seed dormant in the forest floor. 
| When the forest is removed, the temperature of the litter and soil 
| is raised and the seed springs to life. These same factors, with the 
addition of light, cause the seedlings to develop. However, a wide 
| variation of any one of these factors on different sites does not mean 
| that the widely varying factor 1s the one which determines the type, 
_ because other factors, varying less but approaching nearer to the 
_ limit of favorable conditions, may have a great influence on the estab- 
lishment of the seedling or on the germination of the seed. All the 
factors must be taken into consideration, and particularly the limits 
of each under which the seedlings will grow. 
The early development of the seedling is dependent on the food 
stored in the endosperm of the seed. This was demonstrated by 
sowing seeds of western yellow pine, Douglas fir, western hemlock, 
and western red cedar in sand, in soil to which nutrient solutions 
had been added, in potting soil made up of leaf mold and sand, and 
by germinating the seeds in distilled water. The following nutrient 
solution was used: To each liter of water were added 1 gram cal- 
cium nitrate, 0.25 gram potassium chloride, 0.25 gram magnesium 
sulphate, and 0.25 gram acid potassium phosphate. The soil was 
moistened with this solution and watered with it whenever necessary. 
The seeds germinated equally well under all of the conditions, but 
differences were noticeable very soon after germination. Seedlings 
that germinated in the sand came above the ground and appeared 
to be as good as those grown in the potting soil or in the nutrient 
solution until the seed coats were shed; then they began to fail, and 
apparently were unable to get any nourishment or, at least, not a 
sufficient amount to make growth. After the cotyledon stage these 
seedlings did not appear healthy; they either developed their resting 
buds or died. Those in the potting soil and in the nutrient solutions 
made a good growth and did not develop buds until they had passed 
through the regular growing period. Those grown in distilled water 
developed until the food in the seed was exhausted, and then they 
died. 
