RESEARCH METHODS IN STUDY OF FOREST ENVIRONMENT. 91 



It is desired to present another set of data obtained by Bates (105) 

 to illustrate the need of establishing- the wilting coefficient for the 

 particular species in which one may be interested and, therefore, of 

 establishing a specific relationship between the wilting coefficients and 

 the capillary moistures of the same soils. This presentation also 

 assists in showing, what has already been mentioned, that a measure 

 of the capillarity or other moisture relation of the soil has an indirect 

 value in permitting comparisons of the species under a variety of 

 conditions. 



The tests as represented in Table 3 were performed on five distinct 

 kinds of soil, varying as to origin (hence, chemically) and also con- 

 siderably as to composition and water-holding capacity. With the 

 exception of the prairie soil, which contained only 1 per cent of coarse 

 sand and no gravel at all, these soils were prepared by passing 

 through a sieve with quarter-inch meshes. 



The wilting coefficient determinations, moreover, were made with- 

 out the sse of paraffin. As the test was designed particularly to com- 

 pare the four species which were grown in each soil, and it had be- 

 come apparent that the rooting habit of each had a good deal of bear- 

 ing on the stage in soil drying at which it succumbed, the effort was 

 made to keep the upper layer of the soil well supplied with moisture 

 by daily watering. As a result, the common drying of the steam just 

 at the ground line was not appreciably in evidence and, indeed, so 

 general was the drying that the determination of the end point was 

 exceedingly difficult. It was based almost wholly on the flaccidity of 

 the leaves. Whether because of this protection afforded the steins by 

 surface watering, or because of the comparative shade in which the 

 end points were approached, it is noteworthy that the ratios of wilting 

 coefficients to capillarities are much lower, except for the heaviest 

 clay, than in the results obtained under different conditions and 

 already described. 



Another noteworthy feature of this test is that the seedlings were 

 producer] in each soil with the moisture brought daily to the moisture 

 equivalent, so that the availability was, as nearly as could then be 

 calculated, the same in all cases. When drying began, each soil 

 brought by easy stages to two-thirds of the moisture equivalent, 

 and finally to one-third. The seedlings attained an age about f> 

 months before the te-t Was completed. 



