First book of botany : being an introduction to the study of the anatomy and physiology of plants, suited for beginners / by John Hutton Balfour.

  • Balfour, John Hutton, 1808-1884.
Date:
1872
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Licence: Public Domain Mark

Credit: First book of botany : being an introduction to the study of the anatomy and physiology of plants, suited for beginners / by John Hutton Balfour. Source: Wellcome Collection.

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    paper, after maceration. This matter, during the decay of plants, gives rise to the formation of humus, peat, bituminous matter, and coal. The tissue of plants formed of rounded, elliptical, or angular cells is called parenchyma, ■while that formed by spindle-shaped (fusiform) thickened cells constitutes prosenchyma, seen in the wood of trees; and that kind of tissue which is much elongated is denominated vascular tissue. The last-mentioned tissue has its walls formed either simply of cellulose, or of cellixlose and lignine, and sometimes the llgnine occurs in the form of a spiral coil, or of rings or bars. Starch has a similar composition with cellulose. It exists largely in plants. It consists of organised granules, which are insoluble in cold water, alcohol, and ether. When heated with water to about 70° C„ the granules swell up and split, forming a thick pasty mass. Starch granules often exhibit a striated appearance. The stris, or lines on starch gi-ains, are supposed to depend on a wrinkling of the covering. [Starch grains with strife are seen in fig. 11, p. 14.] When starch is heated to about 105° C, and a small quantity of hydro-chloric or nitric acid is added, a substance called dextrine is pro- cured, which has the same composition as starch, and is soluble in water. It is one of the stages of transforma- tion of starch during the progress of vegetable growth. Insoluble starch stored up in cells and vessels is thus converted into the soluble form of dextrine, and this substance is in its turn converted into grape-sugar. By the action of iodine starch becomes blue. Gum (C12H22O11) is another organic substance which is produced by plants. It is seen as an exudation from many plants, such as species of acacia, the cherry, plum, &c. Sugar is another organic constituent of plants, which, like the above substances, consists of carbon combined with oxygen and hydrogen in the proportion to form water. On account of this peculiarity in their composition, these substances are classified as carbo-hydrates. There are two kinds of sugar found in plants, cane-sugar and