Relation of Xonacailable Water to Hygroscopic Coefficient 11 
moisture which the soil was able to absorb from an almost 
saturated atmosphere. He considered this, however, to have 
little practical importance as "by a remarkable coincidence 
the most strongly condensing soils are usually those with 
the highest water capacity and it would probably only cause con- 
fusion if we were to mark these soils with a blemish in 
regard to the supply of water on account of a not very productive 
correction." 1 
Somewhat previous to Mayer, Heinrich 2 had begun a series 
of experiments which were similar to those of Sachs but in- 
cluded many additional precautions to make his results more ac- 
curate aDd employed a larger number of different plants and soils. 
Later 3 he continued his experiments, still further improving his 
methods. The plants were grown in glass vessels of 80 to 100 c.c, 
until they had reached considerable development. The room 
was protected from the direct sunlight and from rapid changes 
of air. the atmosphere being kept almost saturated with water, 
and care being taken to insure the soil being as thickly penetrated 
by roots as possible so that at the conclusion of the experiment 
all parts of the soil would be equally exhausted of water. On the 
wilting of the plants in a moist atmosphere they were quickly 
removed from the soil which was then thoroly mixed for a mois- 
ture determination. The maximum amount of hygroscopic mois- 
ture which the soils could absorb was determined by exposing 
them in thin layers, in some cases for weeks, to a saturated at- 
mosphere. He used six soils, ranging in hygroscopic coefficient 
from 1.15 to 42.30, and found that in no case was the plant able 
to reduce the moisture content to the hygroscopic coefficient be- 
fore wilting. 
To decide whether plants differed from one another in their 
ability to exhause the soil moisture, he used nineteen different 
cultivated plants, including wheat, oats, barley, rye, corn, red 
clover, alfalfa, and potatoes, and also two plants from dry sandy 
soils and one swamp plant. Prom these experiments he con- 
cluded that "Neither the different cultivated plants nor those 
designated as swamp and sand plants differ in their ability to 
extract water from the soil." 
1 Ibid., p. 248. The writer is responsible for the translation. 
2 Heinrich, R. Die Absorptionsfahigkeit der Bodenarten fiir Wasser- 
dampf und deren Bedeutung fiir die Pflanzen. Landwirtschaftliche Annalen 
des mechlenburgischen patriotischen Vereins, Neueste Folge, vol. 15, 187'J, 
pp. 353-358 and 361-363, as abstracted in Biedermann's Centralblatt fiir 
Agrikulturchemie, vol. 12, 1877, p. 16. 
3 Heinrich, R. Zweiter Bericht iiber die Verhaltnisse und Wirksamkeit 
der landwirthschaftlichen Versuchs-Station zu Rostock, 1894, p. 29. 
