114 SEEDING AND PLANTING 



As a rule, the most favorable conditions for germination are 

 attained when the seed is placed in soil kept at a suitable degree 

 of temperature and moisture. The air between the soil particles 

 provides an ample supply of oxygen. Garden soil or other soil 

 containing a large percentage of organic matter is an unfavorable 

 medium due to the various destructive fungi that are dormant in 

 it. As germination proceeds these fungi destroy the seedlings 

 or entirely check their development. Sterilized soil or porous, 

 moderately fine sand is better and should be used in preference to 

 ordinary soil. 



24. GERMINATION TESTS IN SOIL. The soil test is the most 

 satisfactory because it is the natural method and gives the most uni- 

 form results. Other tests often give higher but more fluctuating 

 results and require less time for germination. All germination 

 investigations on an extensive scale should be by soil test. The 

 results obtained are closer to those actually obtained in the nursery 

 and field. When many tests are made, hothouse facilities are 

 essential so that the heat, light, moisture, and air can be easily 

 regulated. The tests can be conducted in small beds made on the 

 benches or in suitably constructed flats. Movable flats have the 

 advantage of being more easily emptied and refilled with soil. In 

 either case the soil should be of uniform depth, usually 4 inches, 

 and thoroughly homogeneous in physical and chemical characteris- 

 tics. The seed is usually covered to a depth equal to its greatest 

 diameter. Bates 1 recommends that all seed be covered to a depth 

 of j inch, that the same soil never be used for two consecutive 

 tests and that special attention be given to securing a uniform 

 depth of soil both under and over the seed (Fig. 18). 



The problems of seed testing are complex and permit of exceed- 

 ingly diverse results depending upon the methods and conditions 

 under which the tests are made. Soil tests in suitably constructed 

 hothouses are now accepted by the U. S. Forest Service as the 

 most useful and are chiefly followed in determining germination 

 values. 



In the pot test an ordinary flower pot is filled with soil and the 

 seed scattered over the surface. A covering of sand is scattered 

 over the seed, or if it is very small and delicate as in willow and 

 birch it is covered with a layer of sphagnum moss or a piece of 



1 Bates, C. G.: The technique of seed testing. (Proc. Soc. Am. For., 

 vol. VIII, pp. 127-138. 1913.) 



