igoo-i.] Effects of Water on Foliage Leaves. 243 



then recognized power of leaves to absorb, and it would be well to give 

 the words of Treviranus — " Man muss daher wie ich glaube eine 

 Einsaugung von tropfbarer Fliissigkeit durch Blatter nur da zulassen, 

 wo entweder die Oberhaut fehlt oder, wie bei, unausgebildeten und 



ueberhaupt bei zarten Blattern sehr diinn ist." "Nur Dunst 



wird eingesogen." 



Two rather important papers by Garreau (1849, 185 1) appeared 

 later, the first of which dealt with this question of water-absorption. 

 Garreau goes into the matter thoroughly and examines this question 

 from the standpoint of anatomy, as well as that of physiology, and 

 concludes that water can be absorbed. One ought to draw attention 

 to the fact that do absorb and caii absorb are two different things, a 

 point which will be discussed in the chapter dealing with water- 

 absorption. 



Hugo von Mohl (1852) gives but little attention to the subject, but 

 states in a somewhat general way that water-vapour is absorbed. It is 

 important to notice that the view here expressed by von Mohl was 

 a cautious one, and that it was now considered by no means certain 

 that water-absorption was a function of leaves. Then came the work of 

 Duchartre (1861, p. 109), whomi one might call the founder of the 

 position taken by writers of modern text books in regard to absorption 

 of water by leaves. One finds Duchartre's work almost always referred 

 to, while the works of several others of no less importance seemingly 

 ignored. One reason probably for this is that Duchartre had performed 

 his experiments with growing plants ; while most of those holding 

 opposite views had based their conclusions upon experiments with 

 detached leaves and cut shoots. Moreover, Duchartre held that the 

 moistening of a leaf surface by rain or dew only caused a diminished 

 transpiration, which resulted in an increase of turgor ; and stated also 

 that as transpiration was a normal function of leaves it was not easy 

 to see how absorption could also be a normal function at the same 

 time. 



Important special papers upon the subject then began to appear, 

 notably that of Cailletet (1872, p. 242), who showed by means of a 

 manometer that water was readily absorbed under certain conditions ; 

 and Boehm (1877) who placed leaves (not detached) of seedlings under 

 such conditions in which it was possible for them to absorb water to 

 advantage when, under like conditions, the roots were unable to do so. 

 The works of Mer (1878, p. 105) and Boussingault (1878, p. 289) 

 corroborated those of Cailletet and Boehm. The work of Henslow 



