804 MODIFICATIONS OF ASPECTS OF ORGANIC NATURE 



from the leaves ; or is it due in the Coniferae to the action of the thousands of points 

 which the whorls of their leaves develop every year? This is a complex question 

 ichich the present data of physical science do not enable us to answer. One thing one 

 can say, and that is that the transpiration of tlie leaves cannot by itself produce this 

 phenomenon. For, as a matter of fact, the transpiration in Coniferae is less active 

 than it is in broad-leaved trees. This fact has been made clear by M, Grandeau in 

 his "Essais historiques et critiques sur la Thdorie de la Nutrition." (M. Fautrat 

 might have added, 'as also by Hales, cit. Boussingault, "Ann. Chim. et Phys." sdr. v. 

 torn. xiii. 1878, p. 314, and Sachs, "Handbuch der Exp. Physiologic der Pflanzen," 

 1865, p. 225.') It then follows that if the vapour of water dissolved in such great 

 abundance in the atmosphere enveloping the pines was the result of the evaporation 

 from the trees, this phenomenon ought to be much more striking over the mass made up 

 by the broad-leaved trees than in that made up by the Coniferae, whilst observation 

 shows that exactly the contrary is the actual fact. We must therefore ascribe to the 

 soil and to other unknown causes this remarkable property which pines have of 

 attracting watery vapour.' 



If it had appeared from M. Fautrat's tables that this excess of 

 watery vapour was more marked in rainy than in dry times, it 

 would have been easy to explain the fact by figuring* to ourselves 

 the all but infinite area which the fine films of water clothing every 

 needle-shaped leaf of a coniferous tree would make up and offer for 

 evaporation. For the leaves of our common Coniferae wet readily ; 

 and it is owing to this property I apprehend that they intercept as 

 much as one-half the rain which falls upon them before it reaches 

 the ground, whilst broad-leaved trees intercept but one-third. But, 

 as it appears, the Coniferae possess the hygrometric advantage inde- 

 pendently of the rainfall. And I have to say that the phenomenon in 

 question, needing, as it thus confessedly does, some additional explana- 

 tion besides and beyond that which our usually accepted views furnish, 

 appears to me to become more intelligible by reference to the theory 

 as to ' The Cause of Rain and its Allied Phenomena ' which was put 

 before the world in 1839, and subsequently published in a separate 

 volume twenty years later, by Mr. G. A. Rowell. This .theory may 

 I think be stated as follows, the author of it having slightly modi- 

 fied it in 1872, and restated it in a 'Brief Essay on Meteorological 

 Phenomena,' published in 1875. He supposes that the molecules 

 of watery vapour are completely enveloped in a coating of electricity, 

 to which they owe their buoyancy. This coating and this buoyancy 

 he supposes to increase and decrease in ratio with the temperature 

 of these molecules. EflScient conduction therefore of electricity will 

 suffice on this theory to precipitate watery vapour either as rain, or 

 as dew, or as mist. And I apprehend that Mr. Rowell would, in 



