Insectivorous plants . itschke has discussed examined the colouring matter this subject in Bot. Zeituug, ?with the spectroscope, and in- 1861, p. 241, &c. See also Dr. forms me that it consists of the Warming (Sur la Difference eutre commonest species of erythro- les Trichomes, &c., 1873;, who phyll, which is often met with in gives references to various publi- leaves with low vitality, and in cations. See also Greenland and parts, like the petioles, which Trtcul, * Annal. des Sc. nat. bot. carry on leaf-functions in a very (4tli series), torn. iii. 1855, pp. imperfect manner. All that can 297
Insectivorous plants . itschke has discussed examined the colouring matter this subject in Bot. Zeituug, ?with the spectroscope, and in- 1861, p. 241, &c. See also Dr. forms me that it consists of the Warming (Sur la Difference eutre commonest species of erythro- les Trichomes, &c., 1873;, who phyll, which is often met with in gives references to various publi- leaves with low vitality, and in cations. See also Greenland and parts, like the petioles, which Trtcul, * Annal. des Sc. nat. bot. carry on leaf-functions in a very (4tli series), torn. iii. 1855, pp. imperfect manner. All that can 297 and said, therefore, is that the hahs 6 DROSERA ROTUNDIFOLIA. Chap. 1. part, which alone is capable of movement, consists of a prolon-gation of the leaf; the spiral vessels being extended from thisto the uppermost part. We shall hereafter see that the ter-minal tentacles of the divided leaves of Eoridula are still inan intermediate glands, with the exception of those borne by the extreme. Fig. 3. {Drosera rotundifolia.) lA>ngitudlnal section of a gland ; greatly magnilied. From Dr. Warming. marginal tentacles, are oval, and of nearly uniform size, 5^*0 of an inch in length. Their structure is remarkable,and their functions complex, for they secrete, absorb, and areartcd on by various stimulants. They consist of an outer layerof siiijill iK)lyg()nal cells, containing purj)le granular matter orlluid, and ^\ith the walls thicker than those of the pedicels. Chap. I. STKUCTUEE OF THE LEAVES. 7 Within this layer of cells there is an inner one of differently-shaped ones, likewise filled with pnrple fluid, but of a slightlydifferent tint, and differently affected by chloride of gold. Thesetwo layers are sometimes well seen when a gland has beencrushed or boiled in caustic potash. According to Dr. Warming,there is still another layer of much more elongated cells, asshown in the accompanying section (fig. 3) copied from hiswork; but these cells were no
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