1906.] PUBLIC DOCUMENT— No. 33. 129 



Influence of Soil Decoctions on Seed Germination. 



Some attempt has been made in the following experiments 

 to ascertain tlie cause underlying the ellects which sterilized 

 soil has on seed germination. The question has often arisen, 

 In what manner does soil sterilizing aflect seed germination ? 

 Is the cause underlying this form of stimulation a mechanical 

 one, or a chemical one? In all probability both mechanical 

 and chemical factors play a role here. If, however, the 

 stimulus is of a chemical nature (and such types of stimula- 

 tion are common enough to seeds) , we would expect some 

 response to occur on the part of the seeds when treated with 

 decoctions of sterilized soils. For special reasons we there- 

 fore selected two types of soils, one of which was a typical 

 Amherst loam, fairly rich in organic matter and suitable for 

 greenhouse culture ; the other soil a yellow loam of the 

 nature of an Amherst subsoil, deficient in nitrogen and con- 

 taining only a slight amount of organic matter. Three sets 

 of experiments were carried out with each soil. In each set 

 there was a boiled loam and subsoil, a sterilized loam and 

 subsoil, and a normal loam and subsoil. The boiling and 

 sterilizing lasted fifteen minutes, the latter being mostly 

 done in an autoclave, under fifteen pounds pressure and at a 

 temperature of 250*^ F. In all cases 400 grams of soil were 

 employed. The soils, were placed in percolators, with 

 500 c.c. of distilled water, and allowed to stand for twelve 

 hours and to percolate very slowly. Four hundred grams 

 of normal loam and subsoil, that is, soil that is not treated, 

 were percolated in the same manner as the others. In addi- 

 tion to the above tests, tap water cultures were employed as 

 checks, and run parallel in every way to the others. 



In some instances, however, distilled water was used, 

 besides the tap water, but since no difference existed between 

 them, the distilled water tests were discontinued. After a 

 percolate had been obtained for the various soils, the seeds 

 were soaked in them for six hours, and then placed in ger- 

 minators of the Zurich type, or into germinators composed 

 of flower pot saucers provided with filter paper. In one or 

 two instances the soy bean was germinated in sawdust. 



