CHAP, ii.] of Plants. Rcichel. 485 



owing to its careful notices of the literature, and the author's 

 original researches in phytotomy. Reichel was not satisfied with 

 the arguments of Malpighi, Nieuwentyt, Wolff, Thiimmig and 

 Hales for the view that the vessels of the wood contain air. 

 He observed quite correctly, that if branches are cut off from 

 woody and herbaceous plants and the cut surfaces are placed 

 in red decoction of brazil-wood, the red colouring matter spreads 

 through all the vascular bundles, even those of the flowers and 

 fruit ; but on examination with the microscope he found the 

 red fluid to some extent in the cavities of the vessels, and 

 hastily concluded that they too in the natural condition convey 

 sap and not air. His description and his drawing show 

 however, that only some vessels had received any of the 

 red fluid and that none of these were filled with it. Reichel 

 and the many who repeated his statements forgot to ask 

 whether the vessels had contained air or fluid before the 

 experiment, or whether the result would have been the same, 

 if plants with uninjured and living roots had absorbed the 

 coloured fluid, and no divided vessels had therefore come 

 in contact with it. There was no reason why observers of 

 that day should not have been alive to the simple consider- 

 ation, that the vessels of a branch parted from the stem and 

 placed in a fluid must necessarily show the capillary action of 

 narrow glass tubes if they are filled with air in their natural 

 condition, and that in the experiment the transpiration of the 

 leaves must favour the ascent of the red juice in the cavities of 

 the vessels, as was to be gathered from other and better ex- 

 periments made by Hales. But these obvious reflections were 

 not made ; the supposed results of the experiment were heed- 

 lessly accepted, and the unfounded notion, that vessels are 

 natural sap-conducting organs, was set up in opposition to the 

 trustworthy decision of Malpighi and Grew, that they convey 

 air. Thus on the strength of badly interpreted experiments 

 one of the most important of physiological discoveries was 

 called in question, and a hundred years later there were persons, 



