iqoo-i.] Effects of Water on Foliage Leaves. 259 



the cell sap in each case ; and also due, perhaps, to different degrees of 

 dififusibility of the substances entering the surrounding water from the 

 leaf; and it may have been due to bacteria. In all cases the juice 

 compressed from similar leaves, at the time of gathering from the plant, 

 and twenty-four hours afterwards, was decidedly acid. Then it is fair 

 to conclude that the leaf juices, or cell sap, did not pass out by 

 mechanical means, or by mere filtration, for then the surrounding water 

 would be acid. This throws some light on the question as to why 

 Duchartre, De Candolle, Ganong and others reached the conclusion that 

 plants, as growing plants, could not absorb water through the leaves. 

 The fact was, that in the washing, spraying or drenching of the leaves, 

 some of the cell contents had been taken out into the water by osmosis ; 

 and so naturally in the resulting weight there would be a slight decrease 

 owing to this loss of substance, though at the same time there may 

 have been water absorbed which the balances could not show, — nay, 

 there must have been if the water used for drenching was pure water. 



That leaves when immersed in distilled water lose a considerable 

 amount of substance, was proved by De Saussure (1805) who made 

 some analyses to determine, not only the nature of the substance 

 extracted by the water, but also the amount actually taken out. He 

 collected some leaves of Corylus on May ist and found that they 

 yielded upon analysis 26 per cent, of dissolved salts which were mostly 

 alkaline. Similar leaves, after being submerged for fifteen minutes in 

 distilled water, yielded only 8.2 per cent, of dissolved salts. The 

 phosphates, he found, were not perceptibly affected by the drenching. 

 De Saussure does not give any details of his analysis of the salt taken 

 out of the leaf by the water, beyond that it is a combination of alkaline 

 salts, — that is to say that they are salts of potassium, calcium, and, it 

 may be sodium. The writer has also found that this substance 

 extracted by water is composed of potassium and calcium carbonates 

 and potassium oxalate, with traces of organic substance. Hence it is 

 found that the residues from the evaporation of the dew-drops, and of 

 this liquid in which the leaves were submerged are practically the same. 



According to Van Tieghem (1898, p. 313) the liquid found upon plants 

 in early morning contains in solution calcium bicarbonate in consider- 

 able quantity. This is the calcium compound absorbed by the roots of 

 plants, according to Roux (1900, p. 331). As it is a very unstable 

 compound, breaking down readily into CaCOs, CO2 and H2O, it is only 

 reasonable to suppose that it is largely through this bicarbonate that 

 the carbonate is found upon leaves in the form of incrustations. From 



