208 HO"\v CKors feed. 



and confined atmosphere in wliich these results were 

 noticed. 



On the whole, then, "\ve conclude from the evidence be- 

 fore us that transpiration is not necessary to vegetation, 

 or at least fulfills no very important oflices in the nutrition 

 of plants. 



The entra'.K-e 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 

 sufiercd 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, Avas then provided, and the 

 pot containing the Avilting plant was supported in it, near 

 its top, while the cylinder was capped by two semicircular 

 plates of glass which closed snugly about the stem of the 

 bean. Tlie jiot of soil and the roots of the plant were 

 thus enclosed in an atmosphere Avhich was constantly sat. 

 urated, or nearly so, with w^atery vapor, while the leaves 

 were fully exposed to the free air. It Avas now to be ob- 

 served Avhether tlie water that exhaled from the leaves 

 could be supplied by the hygroscopic moisture Avhich the 

 soil should gather from the damp air enveloping it. This 

 proved to be the case. The leaves, previously Avilted, re- 

 covered their proper turgidity, and remained Iresh 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 Avater continuously and have no 

 jiower to recover it from damp air (p. 3G) thus giA'cs us 

 demonstration that the clay soil Avhich condenses vapor in 

 its pores and holds it as hygroscopic water, yields it again 

 to the plant, and thus becomes the medium through Avhich 



