CHAPTER III. 



Disputed and Secondary Phenomena op Vegetation. 



Besides the phenomena of vegetation which have been detailed 

 there are other alleged phenomena, the import of which is more open 

 to question : amongst these may be reckoned the absorption of mois- 

 ture by the leaves of plants, the production of water by the plants 

 themselves, and the dropping of water from the leaves of certain 

 trees. 



Sect. I. — On the Absorption of Moisture by the Leaves of Plants. 



It is a prevalent opinion that moisture is absorbed by plants by 

 their leaves. I scarcely open a popular treatise on the subject in 

 which I do not meet with it ; but I have met with no evidence that 

 this is a normal action of leaves, excepting to a very limited and 

 easily defined extent. Abnormal action of leaves absorbing moisture 

 would prove as little as the abnormal absorption of moisture and 

 nutriment into the human frame by enemas and baths; and the absorp- 

 tion of moisture by gigantic algae over the whole surface of their stalks 

 and their fronds proves as little. But this cannot be said of experi- 

 ments which have been made on the growth of epiphytes and of 

 mundane plants, which have grown and flourished when freed of all 

 soil; or of trees growing naturally and at the same time luxuriantly 

 on narrow ridges, on steep declivities, on partially decayed stumps 

 many feet above the ground, on walls of high buildings, and on rocks, 

 in situations where the earth within reach of their roots could not 

 possibly, it is alleged, contain the tenth part of the water which, 

 according to Schleiden and Pfaff, they evaporate in a day. There 

 are, too, forests of great extent on high bluffs and well-drained table- 

 lands where, it is said, " there can exist neither in the subsoil nor in 

 infiltration from neighbouring regions an adequate source of supply 

 for such consumption," 



These are facts established beyond all question; but in regard to 

 what seems to.be the natural conclusion, that in such cases the mois- 



