Methods in Germination Tests of Coniferous Tree Seeds S3 



If it is found that fungi are interfering with the germina- 

 tion of the seeds in sand, some form of sterilization before 

 putting in the seed will be necessary. The use of formalin in 

 the soil is not recommended, since it is v-ery apt to hinder 

 germination. Sulfuric acid, strongly diluted, would undoubtedly 

 be of benefit in checking the fungi, but it will also serve to in- 

 crease the rapidity of germination and thus render seed samples 

 tested in sand treated in this manner not comparable with samples 

 tested in untreated sand. Sterilization with heat will undoubtedly 

 prove the most satisfactory method. 



The writer found that the growth of fungi was inhibited 

 by subjecting the sand to a temperature of 150 degrees C. for 

 forty-five minutes, and since the greenhouse room in which the 

 seed tests were carried on was kept very clean, no reinfection of 

 the sand occurred. Undoubtedly, the physical properties of the 

 sand were slightly changed, but this proved negligible. In the 

 case of loam, however, this change would be marked; in fact, 

 it is not at all unlikely that there would be a noticeable effect on 

 the germination of the seed. 



The depth at which coniferous seed should be placed has 

 been fairly well established. Bates* recommends a covering of 



*Bates, C. C. : Technique of Seed Testing. Proceedings of the S'ociety 

 of American Foresters, 8:131, 132. 



14 inch for all species of coniferous seed so far tested from 

 the central Rocky Mountains, with a slightly heavier covering, 

 y% inch, if desired for Pinus ponderosa seed. Somerville**, 



**Somerville: Experiments with Tree Seed (Bd. Agr. Rpt. Distrib. 

 Grants for Agl. Education in Great Britain, 1894-'95, pp. 62-65. Abstract in 

 Experiment Station Record, 7:509. 



working with Picea e.rcelsa, found that covering the seed to a 

 depth of J4 mcn g ave tne l )est germination per cent. 



In December 1910 samples of Pinus ponderosa seed, col- 

 lected at Maine, Arizona in the fall of 1909, were sown at the 

 greenhouse at the University of Nebraska by the writer in a half 

 and half mixture of loam and sand at various depths. The 

 average temperature of the greenhouse was from 75 to 80 degrees 

 F. for approximately ten hours and then 55 to 60 degrees F. for 

 the remaining 14 hours of the 24-hour period. The table below 

 gives the results. 



