porebueh
Tổng số bài gửi : 5
Join date : 11/07/2011
 | Tiêu đề: That this must be of a very powerful  Mon Jul 11, 2011 3:32 pm | |
| That this must be of a very powerfulThat this must be of a very powerful nature is apparent from the fact, that the smallest leaf at the extremity of the branch of a lofty tree must assist in setting in action the absorbing power of roots, at a distance equal, perhaps, to three thousand times its own length. If this reciprocal action is not maintained without interruption, and if anything occurs to check it during the period of vege¬tation, the plant will suffer in proportion to the amount of interruption. For example, if the roots are placed in a warmer medium than the branches, and are thus induced to absorb fluid faster than the slower action of the leaves can consume it, the superfluous sap will burst through the stem and distend its tissue till the excitability is impaired or destroyed. Or if, on the other hand, a branch is caused to grow in a warm medium, while the roots remain in a very cold medium, the former will consume the liquid sap faster than the latter can supply it, and the consequence will be, MBT that MBT Shoes UK the leaves will die, or the fruit will fall off, or the flowers be unable to set their fruit, from want of a constant and sufficient supply of food; or the fruit will shrivel, or, MBT Shoes as it is said, will " shank." Not that it is necessary for the temperature of the earth and air to be equal, for this does not happen in nature; but it is requisite that they should have some near relation to each other. 69 It is generally, however, believed, that leaves absorb fluid FORMATION OF SECRETIONS. from the air. Their stomates appear well adapted for that purpose, by their position in most abundance on the under side of leaves ; and the possibilit}' of recovering drooping or sickly plants, by syringing their epidermis copiously, seems to render this fact almost ccrtain. It is, however, imagined by some, that leaves have no power of absorbing water, even in an elastic state ; and that the renovation of plants by syringing is merely owing to a diminution of perspiration, which is improbable. | |
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shop89
Tổng số bài gửi : 10
Join date : 16/07/2011
| | Tiêu đề: Re: That this must be of a very powerful Sat Jul 16, 2011 4:32 pm | |
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