Theophrastus[871] informs us, that there is a kind of bulb, which grows on the banks of rivers, and which encloses between the outer coat and the portion that is eaten a sort of woolly substance, of which felt socks, and other articles of dress, are made; but, in the copies, those at least which have fallen in my way, there is no mention made of the country in which it grows, or of any details in connection with it, beyond the fact that the name given to it is “eriophoron.”[872] As to spartum, he makes no[873] mention of it whatever, although he has given the history, with the greatest exactness, of all the known plants, three hundred and ninety years before our time—a fact to which I have already[874] alluded on other occasions: from this it would appear that spartum has come into use since his day. CHAP. 11.—PLANTS WHICH SPRING UP AND GROW WITHOUT A ROOT—PLANTS WHICH GROW, BUT CANNOT BE REPRODUCED FROM SEED. As we have here made a beginning of treating of the marvels of Nature, we shall proceed to examine them in detail; and among them the very greatest of all, beyond a doubt, is the fact that any plant should spring up and grow without a root. Such, for instance, is the vegetable production known as the truffle;[875] surrounded on every side by earth, it is connected with it by no fibres, not so much as a single thread even, while the spot in which it grows, presents neither protuberance nor cleft to the view. It is found, in fact, in no way adhering to the earth, but enclosed within an outer coat; so much so, indeed, that though we cannot exactly pronounce it to be composed of earth, we must conclude that it is nothing else but a callous[876] concretion of the earth. Truffles generally grow in dry, sandy soils, and spots that are thickly covered with shrubs; in size they are often larger than a quince, and are found to weigh as much[877] as a pound. There are two kinds of them, the one full of sand, and consequently injurious to the teeth, the other free from sand and all impurities. They are distinguished also by their colour, which is red or black, and white within; those of Africa[878] are the most esteemed. Whether the truffle grows gradually, or whether this blemish of the earth—for it can be looked upon as nothing else—at once assumes the globular form and magnitude which it presents when found; whether, too, it is possessed of vitality or not, are all of them questions, which, in my opinion, are not easy to be solved. It decays and rots in a manner precisely similar to wood.