458 Theory of the Nutrition [BOOK in. 



After these preliminary remarks he proceeds to prove, that 

 it is in the leaves that the crude juices of nutrition undergo the 

 change which fits them for the maintenance of growth. The 

 way in which Malpighi arrives at this view is as simple as it is 

 original. He considers the cotyledons of young plants to be 

 genuine leaves (in leguminibus seminalis caro, quae folium est 

 conglobatum), as is shown in the gourd, where the cotyledons 

 grow into large green leaves. Liquid is conveyed to them 

 through the radicle, and a portion of the substances which they 

 contain passes from them into the plumule to make it grow, 

 which it will not do if the cotyledons are removed ; hence he 

 concludes that all other leaves also are intended to elaborate 

 (excoquere) the nutritive juice contained in their cells, which 

 the woody fibres have conveyed to them. The liquids mingled 

 together in their long passage through the network of fibres are 

 changed in the leaves by the power of the sun's rays, and 

 blended with the sap before contained in their cells, and thus 

 a new combination of the constituent parts is effected, trans- 

 piration proceeding at the same time ; he compares the whole 

 process with that which goes on in the blood of animals. 



We see that Malpighi's view of the function of the leaves in 

 nutrition approaches very closely to the truth, as closely indeed 

 as was at all possible in the existing condition of chemical 

 knowledge. He was induced by the results of anatomical 

 investigation to carry this view farther and indeed correctly ; 

 he supposed that the parenchymatous tissue of the rind acts in 

 the same way as the leaves ; but he went a step too far in 

 assigning the function of the leaves to the colourless parenchy- 

 ma also, which only serves for the storing up of assimilated 

 matter. He says we must ascribe a character similar to that of 

 the leaf-cells to the corresponding cells in the rind and to those 

 also which lie transversely in the wood (the medullary and 

 cortical rays), and that it is not unreasonable to conclude that 

 the food of the plant is elaborated and stored up in these cells. 

 As he makes no sharp distinction between elaboration and 



