I goo- 1.] Effects of Water on Foliage Leaves. 263 



different. In the calcareous incrustations, the quantity of calcium 

 carbonate is much more pronounced than is the case with dew and 

 guttation water. Under certain conditions guttation water and dew- 

 drops are absorbed by leaves, leaving no deposit of saline matter on the 

 surface of the leaf When the evaporation is rapid a deposit is found. 

 When the drop contains calcium bicarbonate in solution, carbon dioxide 

 is liberated during the process of evaporation. It may be that in desert 

 countries the calcareous incrustations, in the presence of moisture 

 during the night, serve the purpose of retaining the COo given out in 

 respiration. Owing to lack of decomposition of vegetable matter there 

 is a low percentage of COo in the air in deserts. This might indicate an 

 economy of some importance to the plant. 



These results throw some light upon the question of water-absorption, 

 and suggest something in regard to the nature and the cause of such 

 absorption. 



V. — Does Distilled Water Become Alkaline When Placed 

 Upon Leaves of Plants? 



In Sachs' Pflanzen Physiologie ( 1 882, p. 305) he states that if distilled 

 water be placed upon the leaves of plants for a few minutes, it becomes 

 alkaline, and he refers to a paper of his own, (1862, p. 259), upon " The 

 acid, alkaline and neutral reaction of the cell-sap of plants." The 

 subject is merely referred to in his paper, Sachs himself having made no 

 direct investigation into this particular point. The conclusions he 

 draws are based upon work done by Payen and Gaudichaud. These 

 two men entered into a warm discussion, in which Payen held that an 

 alkaline reaction is produced by the leaf, and Gaudichaud showed that 

 the sap of plants in general is acid and rarely, if ever, alkaline. He 

 argued further, saying that the few particular cases mentioned by 

 Payen were irrelevant ; and as no further reply was given by Payen, 

 the matter stood thus for a considerable time. However, in looking 

 into Pay en's work (1848), one finds that he saw far more in the subject 

 than Gaudichaud gave him credit for ; and also that he had the best of 

 the argument as Gaudichaud recognized later on. Payen gave also in 

 connection, some analyses which are interesting. In one of these he 

 found upon evaporating the water taken from Mesembryanthemum 

 crystallinum, crystals of potassium oxalate. A quotation from Gaudi- 

 chaud, (1848, p. 35), gives his position upon the question. "Toutesles 

 autres plantes que j'ai observ^es depuis par ce moyen meme Urticees se 

 sont montrees acides dans le meme espace de temps. On sait que I'eau 

 de ces sortes de macerations devient promptement alkaline. * * * 



