rLANTS DECOMPOSE WATEl. 36 



SECTION V. SOURCE OF THE OXYGEN AM) HYDROGEN OF 

 PLANTS. 



Beside carbonic acid, the leaves of plants absorb 

 through their pores a large quantity of water. During 

 the day when the hot sun is upon them, the evapora- 

 tion is of course far more than the absorption, and in 

 wne the leaves may be seen to droop in the 

 (i; but let the sun be obscured and the atmo- 

 spiiere become misty and damp, and they soon absorb 

 enough moisture to strengthen their failing stems. 

 Every farmer knows that a light shower, which only 

 moistens the leaves without wetting the ground at all, 

 will revive his crops for many hours. Nothing in this 

 case can have be* : ' ' ' »• roote. 



Water, as ha«: I -f oxygen and 



' ! by the plant, 



rvice in mois- 

 tening its various parts and furnishing a circulating 

 fluid, but gives its oxygen or its hydrogen or both, na 

 the plant may happen to require. Water has a pe- 

 culiar adaptation to this purpose, and to others equally 

 useful in the interior of the plant, in the facilitv with 

 which it is .' ( ■ ;,• acid .n? " " r 



(dtemical su! .• with l 



ficulty; but tlif fUmrnt.s ol' water, a substance so 

 universally diffusH and so indispensable, separate 

 easily, affording hydrogen here, oxygen there, to the 

 necessiti*"- "f »'•*• plant. 



SECTION VI. THE NITROGBN OF PLANTS. 



hyd 



one tmnv ot \hv orgnnir b« 



to them: this is nitrogen; r. ;.:...:. 



the mo«t prohahle source of this gas. a. As it fits 



