49 Theory of the Nutrition [BOOK in.
so too he perceives that if bulbs, tubers, and roots, with or without the help of water which they have absorbed, produce shoots and even flowers, this must be done at the expense of material laid up in reserve, but he does not turn this fact to any further account. But he utterly spoilt the best part of his subject ; he made the leaves nothing but pumps that suck up the sap from the roots ; he quotes Malpighi's better view as a curiosity, and never mentions it again ; but he accepts Bonnet's unfortunate theory, though he himself adduces many facts, which make for Malpighi's interpretation of the leaves. He is almost more unsuccessful with chemical points in nutrition ; he repeats Mariotte's statements with regard to the necessity of a chemical change in the nutrient substances in the plant, and even supplies further proof of it ; but he cannot shake off the Aristotelian dogma, that the earth like an animal stomach elaborates the food of plants, and that the roots absorb the elaborated matter like chyle-vessels (II. pp. 189, 230). He concludes from his own attempts to grow land-plants without earth and in ordinary water that the latter supplies the plant with very little matter in solution, but he makes no use of Hales' statements with regard to the co-operation of the air in the building up of the plant, and ends by saying (II. p. 204) that he only wished to prove that the purest and simplest water can supply plants with their food, which his experiments do not prove. Thus almost all that Du Hamel says on the nutrition of plants is a mixture of right observations in detail with wrong conclusions, and reflections which never rise above the individual facts and give no account of the connection of the whole. These faults appear in a still higher degree in a later and almost more comprehensive work, the 'Traite theorique et pratique de la vegetation' of Mustel (1781). The further the distance from the founders of vege- table physiology, the larger were the books that were written on the subject; but the thread that held the single facts together became thinner and thinner, till at last it broke.