CHAP, ii.] of Plants. Major, Malpighi. 457 



fessor in Kiel, first gave expression to the opinion, that there is a 

 circulation of the nourishing substance in plants as in animals ; 

 and from this time to the end of the i8th century the circula- 

 tion of the juices of plants was a favourite subject of discussion, 

 but more often chosen by the impugners of the doctrine than 

 by its defenders. 



The better form of the idea, namely, that there is a return- 

 movement of material towards the root, combined with the view, 

 that the leaves are the organs which produce the substances re- 

 quired for growth from the crude material supplied to them, was 

 expressed by Malpighi as early as 1771 in the shape of a well- 

 considered theory. In his 'Anatomes plantarum idea ' of that 

 year he devotes the last pages to a short account of the theory 

 of nutrition, as he understood it. He regarded the fibrous 

 constituents of the wood as the organs for conducting the sap 

 taken up by the roots, and the vessels as air-passages, which he 

 named tracheae on account of their resemblance to the tracheae 

 of insects. He was in doubt whether the air came from the earth 

 through the roots, or from the atmosphere through the leaves, for 

 he had never succeeded in finding openings for the entrance of 

 air in the roots or the leaves ; but he thought it more probable 

 that the air is absorbed by the roots, because they are well 

 supplied with tracheae, and air has besides a tendency to ascend. 

 Beside these fluid-conducting fibres and air-conducting tracheae 

 in the wood he called attention to the existence of special 

 vessels, which conduct peculiar juices in many plants, as the 

 laticiferous vessels, gum-passages, and turpentine-canals. 



Respecting the movement of the juices, he notices that the 

 direction may be reversed, because shoots planted upside down 

 send out roots into the earth from what is organically their 

 upper end, and grow into trees; and though they do not grow 

 vigorously, yet the experiment proves that the movement of 

 the sap in them is in the reverse direction. 



superstitious belief in the reproduction of plants and animals from their 

 ashes, which was used to prove the re.-urrection of the dead. 



