Page:An introduction to physiological and systematical botany (1st edition).djvu/35

them, unattached to the soil, and nourished by the water in which they float. Some^[1] have characterized Animals as nourished by their internal, and Vegetables by their external surface, the latter having no such thing as an internal stomach. This is ingenious and tolerably correct; but the proofs of it must fail with respect to those minute and simply-constructed animals the Polypes, and the lower tribes of Worms, whose feelers, put forth into the water, seem scarcely different from roots seeking their food in the earth, and some of which may be turned inside out, like a glove, without any disturbance of their ordinary functions. The most satisfactory remark I have for a long time met with on this difficult subject is that of M. Mirbel, in his Traité d'Anatomie et de Physiologie Végétables^[2], a work I shall often have occasion to quote. He observes, vol. I. p. 19, "that plants alone, have a power of deriving nourishment, though not indeed exclusively, from

1. Dr. Alston, formerly professor of botany at Edinburgh.
2. Published at Paris two or three years since, in two vols 8vo.