208 HOW CROPS FEED, 
and confined atmosphere in which these results were 
noticed. 
On the whole, then, we conclude from the evidence be- 
fore us that transpiration is not necessary to vegetation, 
or at least fulfills no very important offices in the nutrition 
of plants. 
The entrance of water into the plant and the steady 
maintenance of its proper content of this substance, under 
all circumstances is of the utmost moment, and leads us 
to notice in the next place the 
Direct Proof that Crops can Absorb from the Soil 
enough Hygroscopic Water to Maintain their Life.—Sachs 
suffered a young bean-plant standing in a pot of very reten- 
tive (clay) soil to remain without watering until the leaves 
began to wilt. A high and spacious glass cylinder, having 
a layer of water at its bottom, was then provided, and the 
pot containing the wilting plant was supported in it, near 
its top, while the cylinder was capped by two semicireular 
plates of glass which closed snugly about the stem of the 
bean. The pot of soil and the roots of the plant were 
thus enclosed in an atmosphere which was constantly sat- 
urated, or nearly so, with watery vapor, while the leaves 
were fully exposed to the free air. It was now to be ob- 
served whether the water that exhaled from the leaves 
could be supplied by the hygroscopic moisture which the 
soil should gather from the damp air enveloping it. This 
proved to be the case. The leaves, previously wilted, re- 
covered their proper turgidity, and remained fresh during 
the two months of June and July. 
Sachs, having shown in other experiments that plants 
situated precisely like this bean, save that the roots are not 
in contact with soil, lose water continuously and have no 
power to recover it from damp air (p. 36) thus gives us 
demonstration that the clay soil which condenses vapor in 
its pores and holds it as hygroscopic water, yields it again 
to the plant, and thus, becomes the medium through which 
