. Elementi di scientifico e agricoltura pratica : O, l'applicazione della biologia e geologia, e della chimica per agricoltura e orticoltura. tances wlien presentato loro.Ma il discriminante e potenza di escrezione è stato dubitato,e queste funzioni della radice non sono ancora completamente stabilito. 2. Stelo o culm. Lo stelo (Fig. 12) è fatta di fasci di tubi delle piccole, che si estende dalle radici alle foglie, in cui sapand la circolazione dell'aria. La corteccia coutains tubi similari per la de-profumo dalle foglie del cambio o succhi elaborati.Lo stelo contiene il midollo c, il quale è costituito da tubi dispo

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. Elements of scientific and practical agriculture : or, The application of biology, geology, and chemistry to agriculture and horticulture. tances wlien presented to them.But the discriminating and excretory power has been doubted, and these functions of the root are not yet fully established. 2. Stem or Culm. The stem (Fig. 12) is made up of bundles ofsmall tubes, extending from the roots to the leaves, in which sapand air circulate. The bark coutains similar tubes for the de-scent from the leaves of the cambium, or elaborated juices.The stem contains the pith c, which consists of tubes disposedhorizontally, and forming by the medullary rays, a communica-tion with the bark ; but so far as experiments have been triedwith colored solutions, the pith does not serve the purpose ofcirculating the sap. The tubes of the wood aid the ascent ofthe sap, which, in its progress upward, is sid)jected lo certainchemical changes, and it is supposed by some that the variousgaseous bodies, which ap in its progress up- DEFINITIONS AND DESCRIPTIONS. 59. ward. The vessels of the wood, Fig. 12. like the roots appear to possess the power of discrimination, as to what substances they will receive. When, for example, the trunks of several trees, of the same species, are cut off above the roots, and immersed in solutions of different substances, some of these solutions will quickly ascend in the tubes, and penetrate the entire mass, while others will not be admitted at all, or very slowly, by the vessels of the tree. The functions of the stem are performed mostly by the alburnum, or sap-wood. The branches or twigs are ex-tensions of the trunk, as a h, Fig. 12. S. Leaves are still further extensions of the wood, and of thebark. The fibres of the leaves are minute tubes of Avoody mat-ter, connected with the w^ood, from which they receive the sap.The green part of the leaf is an expansion of the bark. Thesap descends from this part into the bark, and thence to theroot. Hence, the leaf consists

Parole chiave associate all'immagine

• bookcentury1800
• bookdecade1840
• booksubjectagriculture
• bookyear