The elements of botany : structural and physiological : with a sketch of the artificial modes of classification, and a glossary of technical terms / by John Lindley.

  • John Lindley
Date:
1861
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Credit: The elements of botany : structural and physiological : with a sketch of the artificial modes of classification, and a glossary of technical terms / by John Lindley. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    There is sometimes a great uniformity in the quantity of ashes found in the same plant. Professor Edward Solly found the following quantities in certain Rimbarbs:—viz. iZ/ieitJft tmdulatum, 67 in 10,000 fresh; Jii/Oridum, 68; crin- jmm, 61 ; tataricum, 78 ; Myatts, 62 ; in Asparagus of 1843 from the Horticul- tural Gardens, 700 in 10,000; and in that of 1842, from Co vent Garden, 705. 311. The absolute quantity of mineral matter appears to be connected with the amount of nitrogen, but not the relative quantity. Thus Professor Solly found but 19 parts of ashes in 10,000 of good fir-wood; but 318 in 10,000 when it was rotting ; that is to .say, when the quantity of nitrogen in it gave it a tendency to decay. In like manner the green parts of plants richest in nitrogen are richest in mineral matters. Thus, while timber of oak or deal does not at the worst exceed 320 in 10,000, the leaves of Kidney Beans contain 2!}95, of Chervil 2393, of Celery 2044, &c., as appears from experiments by the same expert analyst. 312. The perfect development of a plant is therefore dependent on the presence of suitable mineral matters ; for when those substances are totally wanting, growth will be arrested ; and when they are deficient, it must be impeded in proportion. For example, corn-plants cannot grow in the absence of silica, and their vigour is, cceteris paribiis, regulated by its abundance. 313. But other substances are required to sustain the life of plants. Phosphoric and sulphuric acids have been found in the ashes of all plants hitherto examined ; and common salt, sulphate of potash, nitrate of potash, salts of iron and copper, chlu7-ide of potassium, and other matters, may be regarded as necessary constituents of several plants. 314. Therefore it is indispensable that every plant should find in the soil in which it grows those inorganic constituents which nature has rendered necessary to it, just as it is necessary for animals that they should find in their food the pliosphates of lime and magnesia, which harden their bones. 315. As soon as food is absorbed, it begins to ascend into the stem, or to diflFuse itself through the system, and receives the name of sap. Lac niveum potes purpureamque sapam.—Ovid. 316. In the course of the sap upwards, water and carbonic acid arc partially decomposed, and their elements are deposited along with nitrogen in the interior of the tissue, forming the protoplasm (G8) or layer over the interior of every cell and vessel, which thus become in part solidified. 317. As soon as the sap reaches the leaves or the surface of the bark, water is rapidly thrown oif, and green matter, or occasionally some other colour, is formed, provided the part is exposed to light. The connection between the apf]-)earance of green colour and lightv is suflRcientlv proved by blanched vegetables, which gain their verdure as soon as light is allowerl to reach them. If some, as Rhubarb, acquire a colour notwithstanding their growth in absolute darkness, that is owing to the presence of sohible colour- ing matter ready formed in the fleshy roots from which the blanched shoots proceed. The loss of water by plants seems to depend mainly (not entirely) upon the inten- sity of light to which they are exposed. In bright sunshine they jierspire most in weak diffused light least, and in darkness not at all. Hales found that a Cabbage lost 19 ounces of its weight per diem, and a Sunflower 20 ; he estimated the average rate of perspiration by plants to be ecjual to 17 times that of a man. In one of his experiments he found that the branch of an Apjile-tree, 2 feet Ion with 20 apples on it, exposed to bright sunshine, raised a column of mercui-v