Soils, their formation, properties, composition, and relations to climate and plant growth in the humid and arid regions

by Eugene W. Hilgard

Fig. 54.—Adobe Soil diluted with sand, 1 to 1.

Fig. 55.—Same, diluted 1 to 3.

DEVELOPMENT OF ROOTS OF WHITE MUSTARD
IN CLAY SOIL, DILUTED WITH VARIOUS
PROPORTIONS OF PURE SAND.

The (“galvanized”) vegetation pots were made as nearly as possible of similar proportions in depth and width for each dilution, so as to give opportunity for the proportional development of the root systems. The photographs show the latter as nearly as practicable in their natural form, restored after washing off the adherent soil. It was of course extremely difficult to preserve intact the extreme circumferential rootlets and hairs; yet the general development is correctly shown.

Fig. 56.—Adobe Soil diluted 1 to 4.

Fig. 57.—Adobe Soil diluted 1 to 5.