. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. DROSEEA EOTUNDIFOLIA. 339 The structure and office of the prehensile and digestive appara- tus are now to be illustrated b\- the following examples : — 889. Drosera rotundifolia, or round-leaved sundew, grows abundantly in northern peat-bogs and in sand mixed with vege- table mould, both in the Old World and the New. The plant has a few (4 to 12) leaves, arranged in a flat tuft at the base of the flower-stalk, and narrowed at their bases into hairy petioles. Th
. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. DROSEEA EOTUNDIFOLIA. 339 The structure and office of the prehensile and digestive appara- tus are now to be illustrated b\- the following examples : — 889. Drosera rotundifolia, or round-leaved sundew, grows abundantly in northern peat-bogs and in sand mixed with vege- table mould, both in the Old World and the New. The plant has a few (4 to 12) leaves, arranged in a flat tuft at the base of the flower-stalk, and narrowed at their bases into hairy petioles. The most striking character of the leaves is the thick clothing of peculiar hairs, otherwise known as tentacles or glands^ from the tip of each of which exudes a drop of a clear viscid liquid. These hairs are complicated in structure. Thej^ contain all the histological elements proper to the leaf itself; for this reason it has been thought by some that they should be regarded as processes from the leaf rather than as hairs. The marginal tentacles are long, have purple stalks, and are terminated by elongated pur- ple glands ; those towards the middle of the leaf are shorter, have greenish stalks and ovoid glands. Each gland consists of a double la3er of polj'go- nal cells which surround a central bod^' composed of elongated cells and a few traeheids. The proto- plasmic lining of all the cells is transparent and thin, and the cavity is filled with an homogeneous purple fluid. The tra- eheids pnss b^- insensible gradations into minute spiral duets. 890. The mode of action in Drosera is as follows: When a small object is placed on the middle glands, a sluggish move- ment is soon detected in the marginal tentacles. If the object is a fragment of animal matter, the motor impulse is commu- nicated rapidly, and the marginal tentacles curve sharpl}- over upon the fragment, bringing the glands in contact with it. The blade of the leaf also sometimes becomes curved, forming a shal- low c
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