CHAP, ii.] of Plants. Malpigln. 459 



mere storing up, he ascribes the function of the leaves to the 

 parenchyma of fleshy fruits also and to the scales of bulbs ; he 

 concludes from the exudations from stumps of trees and from 

 the cut surfaces of other parts of plants, that they are filled with 

 reserve-matter (asservato humore turgent). 



Thus the essential points in Malpighi's theory of nutrition in 

 the year 1671 were, that the vessels of the wood are primarily 

 air-conducting organs, that the leaves elaborate the crude sap 

 for purposes of growth, that the sap so elaborated is stored up 

 in different parts of the plant, and that the fibrous elements of 

 the wood convey upwards to the leaves the crude materials of 

 nutrition which are absorbed by the roots. No mention is 

 made of a circulation of juices, comparable to the circulation of 

 the blood, though this idea was in later times often imputed to 

 him ; and we find by his later remarks, that while he was in no 

 doubt as to the elementary organs which convey the ascending 

 sap, he confined himself to conjecture with respect to the way by 

 which the sap elaborated in the cell-tissue of the leaves, rind and 

 parenchyma generally is carried on its further course. But he 

 was in no doubt about the direction of that course ; he believed 

 that this sap forces itself downwards through the stem into the 

 roots, and upwards in the branches above the leaves and so 

 into the fruit. Thus Malpighi had formed a more correct idea 

 of the movement of assimilated matter than the majority of his 

 successors who introduced the very unsuitable expression, 

 ' descending sap.' He further thought it probable that the 

 elaborated sap passes through the bast-bundles 1 , but without a 

 continuous flux and reflux (absque perenni et considerabili 

 fluxu et refluxu) ; that it rests to some extent in the laticiferous 

 vessels, but that it is also driven sometimes, when occasion 

 requires, by transpiration and external causes into the higher 



1 He says, ' in mediis vasculis reticularibus,' which when taken in con- 

 nection with his general histology, must be understood to mean the bast- 

 bundles. 



