Chap, ii.] of Plant s. Malpighi. 459 



mere storing up, he ascribes the function of the 1< 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 167 1 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. Hut 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 ', but without a 



continuous flux and reflux (absque perenni et considerabiii 



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



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 reticulaiibus,' which when taken in B- 

 nection with his general histology, must be understood to mean ll 



bundles. 



