BOTANICAL GAZETTE 



[JULY 



In this sand the very rapid decrease in the force with which 

 its particles hold water as moisture content increases stands in 

 sharp contrast to the slower decrease in the heavy clay subsoil. 

 While the air-dry sand gives the same kind of result as the air-dry 

 clay, by the time the sand contains 0.44 per cent of water the 

 seeds secure as much water as they do in a molecular solution of 

 non-ionizable salts. This indicates a force of 22.4 atmospheres. 



3. Various soil types. — The results obtained with the subsoil of 

 the Oswego silt loam and the no. 2/0 sand 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, whatever value the wilting coefficient might have. To 

 clear up this point, the soil types of table II were used. Each soil 

 was brought as nearly to the wilting coefficient as possible by 

 addition of water. The closeness of the experimental conditions 

 to the wilting-coefficient determinations is shown in columns 3 and 4 

 of table VIII. 



TABLE VIII 



Relation of wilting coefficient to moisture intake by seeds 



Soil types 



Percentage of 



hygroscopic 



moisture 



Percentage of 

 wilting coefficient 



1. Sand (coarse) 



2. Loam 



3. Sandy loam (very fine) 



4. Loam 



5. Clay loam 



6. Clay loam 



7. Fine sand 



8. Sand (coarse) 



9. Loam 



o. 205 

 3-13° 



210 

 75° 

 218 

 3° 



0.73 ±0.02 

 12. 93=1=0.05 

 8.33±o.o8 



I2.4I ± 0.02 



l6. 12=1=0. OI 



16.34*0.02 

 3. 21*0.03 

 o.83= i =o.oi 



io.S2±o.o6 



The percentage of moisture taken up by dry seeds placed in 

 each soil is shown in the last column of the table. With the excep- 

 tion of the two sands from Yuma, Arizona, which are coarse, the 

 results are fairly uniform. In two cases the soils adhered badly 

 to the seeds, making accurate work very difficult; but corrections 

 were made as carefully as possible. In all the other soils the seeds 

 remained clean, or were easily brushed free of adhering particles. 

 The average intake for the 7 types, excluding the coarse sands, is 



