I4I2 



SOIL PHYSICS, CHEMISTRY AND MICROBIOLOGY 



Experimental Results. 



A. Measurement o/^^e S^g^s. —The data resulting from the measure- 

 ment of the internal forces of Xanthium seeds by means of NaCl and lyiCl 

 solutions are given in Table I and these figures may serve as a basis in 

 the soil experiments, where the surface forces of the soil particles, instead 

 of osmotic pressure are pitted against the internal forces of the seed. 



B. The Surface forces of Soils. — Soil No. 1. The results of 4 of a 

 number of tests made with the subsoil of the Oswego silt loan men- 

 tioned above are shown in Table II. 



Soil No. 2. — The results af a series of tests with the j&ne quartz sand 

 running from air dry (0.14 per cent) to a little beyond the wilting coeffi- 

 cient (1.3 per cent) are shown in Table III. 



Table III. ■ — Relation oj moisture in No. 2 Quartz Sand Moisture 

 Intake oJ Xanthium seeds 



Soil H,o 

 in percentage of absolute weight 



0.14 (air-dry) 



0.159 . . . . 



0.175 . ■ ■ . 



0.203 . . . . 



0.44 . . . . 



0.81 . . . 



1.03 . . . . 



1.49 . . . . 



1.79 . . . . 



2.14 . . . . 



Tntake HjO 

 in percentage of air-dry weight 



0.306 



- 1.407 



5.02 



21.81 



33-98 



42.40 



45.64 

 47.46 

 52.06 

 72.85* 



* Four seeds showing incipient germination, hypocotyls averaging 3 mm. long. 



Various soil types. — The foregoing results suggested that there might 

 be a general relationship between soils and seeds as regards the amount 

 of moisture seeds will absorb at the wilting coefficient of the soil, what- 

 ever value the wilting coefficient might have. To clear up this point the 

 soil types of Table IV were used. Each soil was brought as nearly to the 

 wilting coefiicient as possible by addition of water. 



