16 BOTANICAL GAZETTE [JULY 
B. THE SURFACE FORCES OF SOILS.—1. The Oswego silt loam.— 
A number of tests were made with the subsoil of the Oswego silt 
loam, the results of 4 of which are shown in table V. The air-dry 
soil apparently holds its moisture with about the same force as do 
air-dry seeds, a result one might expect, since both are in moisture 
equilibrium with the same atmosphere at air-dry. 
TABLE V 
RELATION OF SOIL MOISTURE IN SUBSOIL OF OSWEGO SILT LOAM TO WATER INTAKE 
Y SEEDS OF Xanthium pennsylvanicum 
| 
Soil H.0 ntake H:0 oil H:0 In 
in percentage of absolute in percentage - in perentags absolute in percentage of 
weight air-dry weight air-dry weight 
I iit 
. r (ale-dry).: 55... 0.07 5.98 (iraity).o55 235: 0.38 
aw Oeie eta es 3.35 OCIS ei er 1.58 
ee ee, eae eee G225 PGES ea ae S95 
«Bake ge RE SE gar ee 9.58 B06 ches es a 6.16 
05.70) oe ee II.94 M320 oe a 10.76 
R294 a ia eee 17.46 PECOO oc oe 15.70 
4.70: 2 i 20.62 BSTC ee ee 21.36 
O00. oie, 34.00 be ga”. Boas Pare Sepang ah 28.61 
1 de ic, aaa Som as reg eae 20-77 WOUGR pe, a ee 33.86 
ROOF es i eas: 41.79 RO ae es 45-15 
Ds eg Sgr age 46.54 10 3h ie i 49.31 
II IV 
5: : (air-dry) A 0.00 4.65 (air-dry)........ —0.53 
Wea te, 1.91 CM hited ee 8 +1.06 
ie Peas ber eeu es 5.18 7 Bee ys oes 3.68 
ee ee ee ee 6.55 O230 fee oer iawe. cas 6.47 
$0.85 ee eee 9.81 210i ea 10.82 
3.500 ee. 19.93 EA AG ness ae es TS. SL 
2 £29 ee eae 23.88 TS. Ol Giese a 21.11 
OA a ce 31.54 rd We agen oat on fe 32.60 
oe 37-70 74s 41.98 
TF O5 c6c5 7 ose ee 43. Eto Poly Seep an Bee easn Fen 47.26 
be Bay & EPRI ere TAS 43-79 BO ee ee oa 50.00 
As soil moisture is increased, the moisture intake by the seeds 
increases at a much more rapid rate, until the approaching satura- 
tion of the seed begins to cut down the absorption rate. This 
happens as the soil moisture approaches the wilting coefficient. 
Reference to fig. 4 will make the relationship of soil moisture 
content to seed intake clear. 
Sa ON See ee nn See ee Ep ae Serene 
= At EDA Fee nae ee 
q 
4 
i 
3 
4 
% 
