490 Theory of the Nutrition [Book hi. 



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 Hamei 

 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. 



