An introduction to physiological and systematical botany / by James Edward Smith.

  • James Edward Smith
Date:
1814
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to physiological and systematical botany / by James Edward Smith. 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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    and useful to the unexhausted constitutions of children. The same principle accounts for the occasional flowing- of the sap in autumn after a slight frost. Such a pi ema- ture cold increases the sensibility of the plant to any warmth that may follow, and produces, in a degree, the same state of its constitution as exists after the longer and severer cold of winter. Let me be allowed a fur. ther illustration from the animal kingdom. Every body conversant with labouring cattle must have observed how much sooner they are exhausted by the warm days of autumn, when the nights are cold, than in much hot- tei weather in summer, and this is surely from the tmme cause as the autumnal flowing of the vegetable sap.(5) The sap, or lymph, of most plants when collected in the spring as above mentioned, appears to the sight and taste little else than water, but it soon undergoes fermen- tation and putrefaction. Even that of the Vine is scarcely acid, though it can hardly be obtained without (5) [In addition to the above explanation of the flowing of the sap, we may subjoin one which has been suggested, but not enlarged on, by Mr. Knight. In the spring of the year the sap begins to ascend from the root sometime before the expan- sion of the buds. As at this time there are no leaves, flowers, Sec. on which the sap may be expended, the trunk becomes overcharged with it, and will readily bleed if wounded. Afier the leaves are developed, and the growth of the new layer of wood has commenced, all the sap from the trunk is required to afford the material for the new growth, and to supply the pro- digious expenditure by perspiration from the leaves At this period no sap flows from incisions in the trunk. In autumn after a frost has taken place, the functions of the leaves are suddenly checked, the sap is again restricted to the trunk, the vessels are again overcharged with fluid, and will bleed again if divided.]