. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. Cruciferas, Cap-paridaceae, and a few other families are found special cells de-voted to the secretion of enzymes, such as myrosin. The pun-gency of these plants is due to allylic mustard oil, produced, it issaid, at the moment of injury to the plant by the action of my-rosin on the glucoside potassium myronate which is associatedwith the ferment. Glucose and potassium sulphate are otherproducts of this reaction. The digestive glands of insectivorous plants are unique inthat thei
. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. Cruciferas, Cap-paridaceae, and a few other families are found special cells de-voted to the secretion of enzymes, such as myrosin. The pun-gency of these plants is due to allylic mustard oil, produced, it issaid, at the moment of injury to the plant by the action of my-rosin on the glucoside potassium myronate which is associatedwith the ferment. Glucose and potassium sulphate are otherproducts of this reaction. The digestive glands of insectivorous plants are unique inthat their secretions digest animal tissues and are stimulatedto activity by the presence of the captive. On the upper sideof the leaves of Pinguicula are two kinds of glandular hairs,a long-stalked form secreting a sticky mucilage which holdsfast the prey, and a short form, hardly appearing above the epi-dermis, which, when an insect is captured, secretes and poursforth a digestive enzyme (Fig. 115). The short glandular hairson the leaves of Dionaea muscipula behave like those ofPinguicula. 2O6 SECRETION AND EXCRETION. In the pitchers of the genus Nepenthes unstalked digestiveglands occur on the inside near the bottom. These pour forthan abundance of a mucilaginous digestive fluid the water for which is supplied tothe gland by a bundleof tracheids extendingclose up to the base ofthe gland. The most highlydifferentiated glandsare found on the leavesof Drosera rotundifolia(Fig. 105). Here the gland proper, which is borne at the apex of a slender stalk, iscomposed of a bundle of tracheids surrounded by three layersof cells. The outer two layers seem to be especially concernedin producing the secretion. The cuticle is permeable, and ordi- FIG. 115.—Glands from Pinguicula. A, uppersurface of leaf showing long-stalked gland at m, andshort-stalked gland at «. B, cross section through ashort-stalked gland. (A, after Kerner, and B, afterHaberlandt.)
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