ECONOMY OF FARMING. 69 



If some suppose that plants for the production of leaves and stalks need only air 

 and water, they may convince themselves of the contrary in gardens and fields if 

 they will observe salad, cabbage and other leguminous plants, that are planted partly 

 in manured and partly in exhausted beds. The consumption of manure of green 

 plants artd those lipe tor gathering is very different, as we observe by the dillerent 

 power which the fields exert in case half of the field — when the whole is sown with 

 vetches, rye, or any other plants — is mowed green and the other half suffered to 

 ripen. The cause of this appearance lies in part in the longer time which the plants 

 of the last half remain in the field, of which we have already spoken (8) ; in part it 

 must be ascribed to the different necessity of organic nutriment which the plants need 

 for tlie formation of their different parts ; and if they require less humus for the 

 formation of leaves and stalks, yet more is necessary for the formation of the grain ; 

 thereJbre, if we see in poor, yet not wholly exhausted fields, in favorable weather, that 

 the crops are often as large as in stronger fields, this shows the dependence on the 

 humus for the formation of the grains, which under such circumstances are less 

 numerous and smaller in size. Peas in poor fields grow in moister and warmer 

 weather, always showy enough indeed, as to stalks and leaves, but the pods remain 

 mostly empty. Finally, the greater exhaustion of the soil by the production of grain, 

 especially ot the griiss kind of plants, must be sought herein that the leaves begin 

 to dry up as soon as the blossoming is over, and are unfitted for the absorption of air 

 and vaporous nutriment when the grain is formed, which in a great degree must be 

 produced by the nourishment mounting from the roots through the stalk. 



1 1. Plants do not require for that which they have produced from the 

 6eld, and which has been taken away from thence, an equal addition of 

 manure ; because they possess the power to appropriate organic matter in 

 unequal degree, and the quantity of organic remains which they leave in 

 the fields, as decaying leaves and roots, is very different. 



12. The pod-bearing vegetables need generally less manure than the 

 plants of a grass kind ; for, in a given soil, and in a given time, they pro- 

 duce more organic matter than do the latter ; because they absorb a greater 

 quantity of atmospheric and mineral substances. 



We have already proved the correctness of this opinion in the Special Culture of 

 Plants § III. B. p. 76), and refer to those remarks. 



[The observations to which our Author here refers are the following: "Plants can 

 take so njuch the more moisture from the air as the surfece of their leaves collectively 

 is greater, or as they have more absorbing vessels, or hair upon their surface. They 

 dry less easily the thicker their leaves are. and the moisture shut up between them is 

 more slimy or viscous ; and if the plants are connected with many thick or strongly- 

 haired leaves and roots pressing deep into the soil, they all of them must mostly 

 draw a great part of their nourishment from the air, and also resist dryness. 



"The pod-boaring plants have these properties in a higher degree in tliemselves than 

 the grasses. Those with a small root vetches, peas lentils and beans, form them- 

 selves very perfectly, therefore, in a moist climate and an easy soil, with litde manure ; 

 but in a dry climate their roots must be protected by a close soil before drying up, or 

 by a greater quantity of nutriment in the soil, obtain more physical power. Those 

 with deep, penetrating roots, clover, sainfoin, luzerne, endure in the same circum- 

 stances a warmer climate, and greater dryness than if the soil is more clayey and the 

 plants older and the roots penetrate deeper into the soil. The extraordinary great 

 organic production of this last plant cannot possibly be ascribed only to the humus 

 existing in the soil ; since, were it possible that the same field, if it were sown with 

 grain, should produce in a course of 4 years some 150 cwt. of grain and straw, iC it 

 bears luzerne. it produces more than double, often three times this weight in dry 

 leaves and stalks: and how can we explain the luxuriant growth of the white horse- 

 bean, I lip! n IIS alhus, in a poor and light soil, unless we suppose that these plants, by 

 means of tht ir inany large, thick and heavy leaves, suck a great part of their 

 nourisliment from the air, and that their long tapering (pfahlformig) roots, running 

 into the soil, with small horizontal sucker roots, appear to be designed more to suck 

 in water in the depth of the soil, and to protect the plants before drying up, than to 

 suy)^"'ly them with nourishment? 



"Tiic culture of the pod-bearing plants, therefore, exhausts the soil less; and because 



