78 HISTORY OF BOTANY 



ducts, which you know to be intercellular spaces, and 

 both of them with the true vessels of the xylem. In his 

 pages we meet with the old misconception about wood 

 being derived from the rind, while between them lies a 

 nutrient sap in which new cells and tubes are to be found 

 in various stages of formation. 



Four years later, in 1812, a much more important 

 work Beitrdge zur Anatomic der Pflanzen was published 

 by Moldenhawer important not only on account of the. 

 many new histological facts that are recorded in it, but 

 also because it formed the basis of the investigations of 

 one of the greatest of the nineteenth-century anatomists, 

 Hugo von Mohl, with whose work we shall have to deal 

 in due course. To begin with, Moldenhawer introduced 

 a new method in his investigations, viz. that of macera- 

 tion of tissues in water. By this means he was able to 

 isolate cells and fibres and examine them separately 

 under the microscope. He then saw that the views of 

 Wolff, Mirbel, and others, who held that these units 

 appeared like bubbles in a uniform matrix, were quite 

 untenable. The cavities of the cells were seen to be 

 separated from each other by two walls, not one. He 

 was able to demonstrate that fibrous elements were 

 conjoined with vessels in long strands, separated by 

 parenchyma, and thus introduced the term " fibro vascular 

 bundle," so familiar to you. This discovery had far- 

 reaching consequences, for it enabled Moldenhawer to 

 present a new conception of the architecture of the plant 

 organs. The stem of a Dicotyledon was no longer to 

 be regarded as composed of rind, wood, and pith, but of 

 vascular bundles, at first distinct from each other and 

 gradually fusing as age increased. Increase in thickness 

 is thus centred in the vascular bundle, and the ancient 

 idea of a transformation of rind into wood is finally got 

 rid of. Cells, he says, have no holes in their walls, am 

 for the first time a stoma is described correctly. 



It was almost inevitable that he should fall into some 



