28 BOTANICAL GAZETTE [JANUARY 
then, in this ratio a second method of determining the wilting 
coefficient, when the hygroscopic coefficient is known, as follows: 
Hygroscopic coefficient _ wilting cdeflicient. 
OI2 
HEINRICH™ determined the non-available moisture in six types 
of soil, using the wilting points of corn and oats as indicators. He 
TABLE III 
THE RELATION OF THE WILTING COEFFICIENT TO THE HYGROSCOPIC COEFFICIENT IN 
SOILS RANGING FROM SAND TO CLAY 
RaTIO OF 
No. Sor. TYPE Hycroscoric ona chert 
‘O WILTING 
No. dets. Average GORIPICTRR? 
7 DP A aa pie Coarse sand 0.5 II 0.9 0.556 
Opi aes een a Fine sand ea 16 2.6 0.577 
eri ener me rad Fine sand a4 3 3.3 0.698 
Ge eet) ine sand 2.3 2 3.6 0.639 
a ee Sandy loam a8 9 4.8 0.729 
1G CUR OTE ae ae Sandy loam 4.4 3 6.3 0.699 
Sey ine sandy loam oe 13 5.7 0.670 
Eee See es 7 3 10.3 0.757 
By Dea eee Sandy loam 6.3 I 9.9 0.636 
Bese Fine sandy loam 6.6 I 10.8 0.611 
Meee ere Fine sandy loam oe I *r6 0.646 
AO Ge A ee ae ae 12 13.9 A 
Pe Rie eee m 9. I 15.2 0.631 
: 3: Pease aces Clay loam 11.8 2 14.6 oO. 
TA. ioe aie Clay loam 13.2 4 16.2 0.815 
ce el sents S08 Clay loam II.2 I 16.5 0.679 
Dien lay loam 11.4 16 16.3 0.700 
Mean... 0.680 
Probable error of mean......... +0,012 
also measured the hygroscopic coefficient of each soil used in his 
experiments. We have computed from his measurements the mean 
ratio of the hygroscopic coefficient to the wilting coefficient, to- 
gether with the probable error of the mean, obtaining the value 
0.696 0.03, as compared with the ratio 0.68 +o0.o01 obtained from 
our experiments. While Hernricu’s determinations show more 
variation than our own, the ratio obtained from his results agrees 
within the limits of his probable error with the ratio obtained in 
 Herrica, R., l.c. 28-32. 
