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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    alcohol ; when moderately firm, it is coloured blue by iodine, losing tliis colour and becoming yellow by soaking in Avater.—Henfrey. 75. Jelly, (Pflanzeirgallerte—/S'c7i^6'ic?e;«.) A mucilage which is horny and homogeneous when dry, slowly soluble in water, unaffected by iodine : occasionally fills particular cells, as in the stems of certain cacti when it G;ives tlie cells a singular crimveular appearance ; and in the tubercles of Orchis and its allies, when it fills large angular cells with an apparently homogeneous mass, which, however, itself consists of nascent cells. It is the gelatinous matter of Carrageen moss and other Algals, a portion of horny albumen, salej), &c., and is probably the sjime as the Bassorin and Pectin of chemists. Its exact composition is unknown; that of Pectin is said to be C12 H16 Oio.—Mulder. 76. Starch'' °- is the most conspicuous of the cell contents. It occurs in all plants at some period of their existence, and when in the state of grains or granules (80) forms the most positive mark of distinction between plants and animals. 77. When pure its composition is C12 H20 Oio, and it is stained blue or some shade of violet by iodine. This is pronounced to be the true che- mical composition of starch accord- ing to the latest reseai'ches of Berze- lius and Liebig. ^ Its discrepancy with former analyses appears, from the observations of Schleiden, to have been caused by the starch previously examined not having been freed from its impm'ities with sutRcient care. 78. It never occurs perfectly pure in nature, the peculiar secretions of the species being incorporated with its surface. Hence, although chemists find the com- position of pui*e stai'ch to be uniform, natural starch varies in its value as diet, according to the quality of the plant that yields it, as is evident if the action on the stomach of potato starch from a poisonous Solanum, is compared with that of arrow-root, from the insipid inert Marants. Its usual impurities arise from the presence of fatty or albuminous matter, and nitrogenous deposits. 79. It is insoluble in water, but it is readily changed into gum by natural processes, and it disappears under the action of caustic potash. The observations of Schleiden show that although it fonns a bulky mass when ti'eated with water, yet it is ijicapable of passing through a cellular membrane. 80. Starch-grains are found in all cellular parts when full grown, excc])t in the epidermis. They do not occur in young parts, nor in intercellular passages, nor in vessels (which are not secreting organs). They are com- Fig. 59.—Cellular tissue of Cereus variabilis, containing a a jelly; 6 crystals; e starch-griiins.— i>( hidden. Mar. 00.—<i h Cell of a potato containing stai-ch; c starch-grains ai)art; def wheat stiuch in cliiferent positions.