A manual of physiology : including physiological anatomy / by William B. Carpenter.

  • William Benjamin Carpenter
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: A manual of physiology : including physiological anatomy / by William B. Carpenter. Source: Wellcome Collection.

    96/690 (page 64)
    the gigantic Bamboos, which are but Grasses on a large scale, can flourish. 103. It appears, then, that to every species of Vegetable there is a temperature which is most congenial, from its producing the most favourable influence on its general vital actions. There is a considerable difference between the power of grovnng, and of flourishing, at a given temperature. We may lower the heat of ai plant to such a degree, as to allow it to continue to live; yet its condition will be unhealthy. It absorbs food from the earth and; air, but cannot assimilate and convert it. Its tissue grows, but becomes distended with water, instead of being rendered firm by solid deposits. The usual secretions are not formed; flavour, sweetness, and nutritive matter, are each diminished; and the power of flowering and producing fruit is lost. We see a diff'erence in the amount of heat required for the vegetating processes, even in the various species indigenous to our own climate ; thus the' common Chickweed and Grroundsel evidently grow readily at a tem- pei'ature but little above the freezing point, whilst the Nettles, Mallows, and other weeds around them, remain torpid. But the difference is much more strongly marked in the vegetation of dif- ferent climates; showing an evident adaptation of the tribes indi- genous to each, to that range of temperature which they will there experience. Instead of being scantily supplied with such of ihe tropical plants as could support a stunted and precarious life ir ungenial climates, the temperate regions are stocked with a mul- titude of vegetables which appear to be constructed expressly foi them ; inasmuch as these species can no more flourish at the Equator, than the equatorial species can thrive in the Temperate regions. And such new supplies, adapted to new conditions, recur perpe \ tually as we advance towards the apparently frozen and untenant ■ able regions in the neighbourhood of the Pole. Every zone has iti peculiar vegetables; and while we miss some, we find others making: their appearance, as if to replace those which are absent. 104. Thus in the countries lying near the Equator, the vegetatioi consists in great part of dense forests of leafy Evergreen trees, Palms. Bamboos, and Tree-Ferns, bound-together by clustering Orchidea and strong creepers of various kinds. There are no verdani, meadows, such as form the chief beauty of our temperate regions: and the lower orders of Vegetation are extremely rare. It is onlj in this torrid zone, that Dates, Cofiiee, Cocoa, Bread-fruit, Bananas. Cinnamon, Cloves, Nutmegs, Pepper, Myrrh, Indigo, Ebony, Log wood. Teak, Sandal-wood, and many others of the vegetable products most highly valued for their flavour, their odour, their colour, o] their density, come to full perfection. As we recede from th( Equator, we find the leafy Evergreens giving-place to trees witl deciduous leaves; rich meadows appear, abounding with tendei, herbs; the Orchideje no longer find in the atmosphere, and on th(