1004. The earliest systems of classification must have been perfectly natural; as the first step, after giving names to plants to distinguish them from each other, must have been to class them rudely together. As Dr. Lindley observes, ' plants must have yielded man his earliest food, and his first built habitation. Their general use could not fail to produce experience, and especially the art of distinguishing one kind of plant from another, if it were only as a means of recognising the useful and the worthless species, or of remembering those in which such qualities were most predominant. This would involve from the very beginning the contrivance of names for plants, together with the collection of individuals into species; and the mental process by which this was unconsciously effected, gradually ripened into the first rude classifications we know of. By placing together individuals identical in form and the uses to which they could be applied, species were distinguished ; and by applying a similar process to the species themselves, groups analogous to what we now call genera were obtained. The last step was to constitute classes, which were recognised under the well-known names of 'grass and herbs yielding seed, and fruit trees yielding fruit.'' (Lindley's Vegetable Kingdom, Introd. p. xxii.)
