. A textbook of botany for colleges and universities ... Botany. Fig. 636. — Young resin gland of fir {Abies): ti, duct, an intercellular space formed by the sepa- ration of the four nucleate cells. — After Tschirch. This hypothesis is clearly inapplicable to secretions which are not miscible with water, like essential oils and resins. They are probably formed, however, in the very wall itself, and thus the material may not have to traverse the ecto- plast as resin or oil. Unfortunately, even the place of their origin is still obscure. R61e of certain secretions.—Nec- tar is gathered by many i
. A textbook of botany for colleges and universities ... Botany. Fig. 636. — Young resin gland of fir {Abies): ti, duct, an intercellular space formed by the sepa- ration of the four nucleate cells. — After Tschirch. This hypothesis is clearly inapplicable to secretions which are not miscible with water, like essential oils and resins. They are probably formed, however, in the very wall itself, and thus the material may not have to traverse the ecto- plast as resin or oil. Unfortunately, even the place of their origin is still obscure. R61e of certain secretions.—Nec- tar is gathered by many insects, some of which store it, after partial digestion, as honey. While the floral glands are being explored for nectar, the visitors become dusted with pollen and transfer this to ripe stigmas of the same or other flowers, thus insuring pollination in many cases where otherwise it might not occur (see Part III on pollination). The role of extrafloral nectar is not clear. Digestive glands, most defi- nite in insectivorous plants (p. 386), secrete enzymes (p. 399) by which the soft parl< of captured insects are dissolved. Essential oils (p. 413) sometimes prevent plants from being eaten by Fig. 637. —Oil receptacle (a) in orange (Cit- rus Aurantium), formed partly by splitting, but chiefly by destruction of secreting cells and their neighbors (0; 0, 0^ drops of essential oil. — After Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928; Barnes, Charles Reid, 1858-1910, joint author; Cowles, Henry Chandler, 1869- joint author. New York, Cincinnati [etc] American book company
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