82 Forest Club Annual 



greenhouse. Some difficulty was encountered with fungi grow- 

 ing on the filter paper, which retarded germination of the seed, 

 but on the whole, the results were satisfactory for this method 

 of testing. 



As a rule, however, the soil test will undoubtedly prove the 

 most satisfactory for all round results since it is the most 

 natural method of germination, thus giving a closer relation to 

 field results ; and also standarization under this method will be 

 easier to attain. The United States Forest Service has formally 

 adopted the soil test for coniferous tree seeds. 



Occasionally sawdust has been recommended instead of 

 soil, but this does not seem to have any strong points to recom- 

 mend it and has one serious drawback. The leaching out of 

 chemicals from the sawdust under the influence of moisture may 

 retard or entirely stop germination, the presence of tannic acid 

 being particularly fatal to germination through poisoning of the 

 \oung radicle. 



The choice of the kind of soil to use is another important 

 point. The germination of seeds is dependent on the physical 

 rather than the chemical properties of soil, although the latter 

 cannot be disregarded. Pure sand is generally accepted now 

 since it has the advantages over loam ( 1 ) of draining more easily, 

 (2) not crusting so easily (crusting seriously retards germina- 

 tion), (3) not packing so hard, (4) more easily securing a uniform 

 soil texture throughout the flat or till, (5) conducing less to the 

 growth of fungi and algae, (6) being less affected, if at all, as lo 

 its physical properties when necessarily sterilized with dry heat 

 at a temperature of 150 degrees C., (7) being more free from 

 soluble chemical matter that may be of influence. 



During 1910-1911 an experiment was carried on by the 

 writer in the greenhouse at the University of Nebraska to de- 

 termine the effect of different soils on the germination of 

 Pscudotsuga ta.vifolia seed of unknown origin. One sample was 

 germinated in pure sand, another in a half and half mixture oi 

 sand and loam, and a third in loam soil. Germination, in the 

 first instance, commenced in eight days, in the second in ten days 

 and in the third in twelve days with a final germination of 75 

 per cent, 70 per cent and 67 per cent respectively at the end of 

 146 days. A blotter test in a moist chamber for this seed at the 

 same time yielded a final germination of 75 per cent in 42 days, 

 identical with the final germination in sand in 146 days. 



The difference in the final germination in these three cases 

 is not p;reat, but still large enough to be at least suggestive that 

 sand is the most valuable medium for this species. 



