Tổng số bài gửi : 5
Join date : 11/07/2011
|Tiêu đề: Among the experiments of M. Garreau Mon Jul 11, 2011 3:31 pm|| |
Among the experiments of M. Garreau Among the experiments of M. Garreau to which allusion has been already made, was one on the relative amount of perspiration by the two surfaces of ordinary foliage. Leaves growing on healthy plants were selected, and a circular portion inclosed between two closely fitting glass receivers, so MBT Shoes UK arranged that the leaf formed the division between the two glasses—the upper surface was in the one glass, whilst the under surface of the leaf was in the other. The quantity of moisture given off was ascertained by placing in each glass a weighed portion of dry chloride of calcium, which, being very greedy of moisture, would absorb all the vapour as fast as the surface of the leaves gave it out. The result of this experiment was that the lower surface of leaves gives off, from an equal quantity, three times as much as the upper surface; sometimes the proportion was as high as five to one; and the ratio was independent of the position of the leaf itself. This exhalation of water has some connection with the number and size of the stomates, but is by no means wholly dependent on it, as there is evidently a large quantity of water given off independently of them. The evaporation is most abundant along the MBT course of the nerves, and in those parts of the epidermis, on wliich there is the least quantity of oily matter. Hence it is apparent why carefully washing with soap and water proves so beneficial (see p. 58). The operation increases greatly the power MBT Shoes of evaporation. 68 All such experiments teach us that under ordinary circumstances the growth of a plant causes the formation and development of certain substances. which in time fill up its pores, check perspiration, and consequently interfere with the nourishment and further growth of the plant.
Tổng số bài gửi : 10
Join date : 16/07/2011