A new system of vegetable physiology : designed to account satisfactorily for the phenomena which take place in the vegetable kingdom, and to shew the influence of heat, light, and electricity on vegetation / by Daniel Vaughan.

  • Vaughan, Daniel, 1821-1879.
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: A new system of vegetable physiology : designed to account satisfactorily for the phenomena which take place in the vegetable kingdom, and to shew the influence of heat, light, and electricity on vegetation / by Daniel Vaughan. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    convert the dissolved humus into woody fibre. Nature appears to have designed the leaves for the special purpose of the elaboration of the sap; but instead of conveying it to them, and again transmitting it, in its al- tered state, to the various parts of the tree, she has adopted a more sim- ple and effectual method for accomplishing the same purpose. The evaporation from the leaves, gives rise to the excitement of negative electricity; and this, through the conducting medium of the fibres,or the moisture they contain, tends to consolidate the sap, causing, per- haps, at the same time, a slight deoxidation. In spring, when the leaves are absent, and evaporation is almost suspended, the juice of the maple affords sugar. In April, when evaporation begins to take place to some extent, from the newly formed leaves, the gradual conversion of sugar into wo^dy fibre, is marked by the viscidity of the syrup. During the summer, when great evaporation takes place from the leaves, there is a continual formation of woody fibre. In the end of autumn, the for- mation ceases, and the presence of sugar can now be recognised in the sap. I shall now consider more minutely the manner in which these changes are effected, all of which can be traced to the influence of electricity. 39. It appears, from a chemical analysis of starch, gum, sugar, and the cellular fibre of wood, that they are all composed of the same ele- ments, united in nearly, or, perhaps, exactly the same proportions.— The atomic composition of each, may be represented by the formula C.12, O.10, H.10 ; and woody fibre differs little from them in composi- tion, containing less oxygen and hydrogen. Several parts show that these substances are mutually convertible into each other]; and saw- dust has been actually converted into starch, by either of the following methods : 1st. by being heated several times in a baker's oven. 2d. By the action of strong sulphuric acid. 3d. By the action of hydrate of potash. In the first method, the change of the sawdust seems due to the absorbtion of vapor from the air, on account of its capillary attrac- tion. In the second case, the conversion is attended with no decom- position of the sulphuric acid, and is caused by the absorbtion of mois- ture from the atmosphere, by the condensation experienced in its union with water, and by its electrical state, to which I will shortly refer. In the third, the change may be traced to the condensation of vapor; and, perhaps, of carbonic acid, which potash absorbs from the air. It may be observed, also, that starch or sawdust may be converted into sugar by the action of sulphuric acid ; and the change appears to depend on the same principle of condensation—or positive electricity. Potash and lime appear to act in like manner, in the purification of sugar, as it has been shown, by M. Pelouze, that the carbonic acid which the lime absorbs, is principally derived from the atmosphere. On the con- trary, the deterioration which sugar suffers, when the evaporation of tne syrup is conducted at a low temperature, or in the open air, seems owing to its partial conversion into starch, or woody fibre; and a change of the same nature is apparent, when the extractive matter of vegeta- bles is rendered insoluble under similar circumstances. 40. Sugar, vegetable extract, starch, gum, and woody fibre, may be regarded as the same vegetable matter, in different states of electric^