58 NEHEMIAH GREW 



transitions between the former and leafy branches 1 . There is 

 no reason to suppose, however, that our author was acquainted 

 with the work of Albertus. Grew realised the nature of Bulbs, 

 and points out that " the Strings only, are absolute Roots ; 

 the Bulb, actually containing those Parts, which springing 

 up, make the Leaves or Body ; and is, as it were, a Great Bud 

 under ground." 



Nehemiah Grew was interested in plant physiology, although 

 the state of chemical and physical knowledge at the time did 

 not allow of his advancing so far in this, as in the morphological 

 side of the subject. His turn of mind, too, appears to have 

 naturally led him to the study of form rather than that of function. 

 As regards the absorption of water, his idea was simply that 

 the roots sucked up water like a sponge, because the parenchyma 

 was of a spongy nature. He supposed that the liquid was 

 rendered purer by being strained through the skin, which, accord- 

 ing to whether it was of a texture resembling brown paper, 

 cotton, or leather, would produce a different effect upon any 

 solution passing through it. His explanation of the ascent of 

 the sap had really much in common with the "Kletterbewegung" 

 theory propounded by Westermaier 2 almost exactly two hundred 

 years later. Grew argued that " considering to what height and 

 plenty, the Sap sometimes ascends ; it is not intelligible, how 

 it should thus ascend, by virtue of any one Part of a Plant, 

 alone ; that is neither by virtue of the Parenchyma, nor by virtue 

 of the Vessels, alone." He pointed out that the parenchyma 

 might suck up a liquid for a short distance, and also the vessels, 

 like " small Glass-Pipes immersed in Water, will give it an 

 ascent for some Inches ; yet there is a certain period, accord- 

 ing to the bore of the Pipe, beyond which it will not rise." To 

 account for the rise he supposes that the vessels and parenchyma 

 work together, the turgidity of the surrounding parenchyma 

 cells both compressing the vessels, and thus causing the liquid 

 in them to ascend, and also actually forcing some of their own 

 contents into them. 



1 Ernst H. F. Meyer, Geschichte der Botanik, vol. iv. p. 60, 1857. 



2 M. Westermaier, "Zur Kenntniss der osmotischen Leistungen des lebenden 

 Parenchym's." Ber. d. deutsch. hot. Gesellsch. Bd I. p. 371, 1883. 



