Page:An introduction to physiological and systematical botany (1st edition).djvu/389

 Rh great advantage even to chemistry itself, now become so vast and accurate a science. Independently of all general methods of classification, whether natural or artificial, plants, as well as animals, are distinguished into Genera, Species, and Varieties.

By Species are understood so many individuals, or, among the generality of animals, so many pairs, as are presumed to have been formed at the creation, and have been perpetuated ever since; for though some animals appear to have been exterminated, we have no reason to suspect any new species has been produced; neither have we any cause to suppose any species of plant has been lost, nor any new one permanently established, since their first formation, notwithstanding the speculations of some philosophers. We frequently indeed see new Varieties, by which word is understood a variation in an established species; but such are imperfectly, or