ABSORPTION OF WATER. 67 



leaves are very flaccid and dry, the air being at the same 

 time very moist, but that it does not take place when the 

 leaves are in their ordinary condition. The freshening effect 

 which is produced when plants which are beginning to wither 

 are introduced into a moist atmosphere is to be attributed to 

 the consequent diminution of loss of water by transpiration. 



Inasmuch as the leaves of land-plants can absorb water 

 under certain special conditions, it is natural to infer that 

 they can also absorb substances in solution. This has been 

 proved experimentally by Boussingault and by Mayer. The 

 former found that if a drop of a solution of calcium sulphate 

 be placed on a leaf, both the water and the salt will disappear 

 in the course of a few hours, and sooner on the lower than 

 on the upper surface ; the latter obtained similar results with 

 a solution of ammonium carbonate. 



It appears, then, that, under certain conditions, the foliage- 

 leaves of land-plants will absorb water and substances in 

 solution. It must, however, be borne in mind that any part 

 of a plant if immersed in water will absorb a larger or smaller 

 quantity of it. It is a common experience that cut flowers 

 or branches when placed with their cut surfaces in water will 

 absorb for a time sufficient water to prevent withering. The 

 evidence before us is insufficient to prove. that the absorption 

 of water is an important normal function of leaves. Their 

 true absorbent function will form the subject of the next 

 lecture. 



BIBLIOGRAPHY. 



Sachs; Landwirthschaftliche Versuchs-Stationen, I, 1859, and II, 



1860. 



Way ; Journ. Roy. Agricultural Soc., XI, 1850, xill, 1852, XV, 1854. 

 Henneberg und Stohmann ; Journ. f. Landwirthschaft, 1859. 

 Unger ; Anat. u. Physiol. d. Pflanzen, 1855. 

 Chatin ; Botanische Zeitung, 1858. 

 Solms-Laubach ; Die Ernahrungsorgane parasitischer Phaneroga- 



men, Jahrb. f. wiss. Bot, VI. 



Nobbe; Landwirthsch. Versuchs-Stat, VI, 1864, and IV, 1862. 

 Vesque ; De Tinfluence de la temperature du sol sur 1'absorption, 



Ann. sci. nat., se>. VI, vol. 6, 1878. 

 id. ; L'absorption compare'e a la transpiration, ibid. 



52 



