ORGANS OF AERATION. 101 



the form of a spindle *, which he supposes to serve 

 as reservoirs for the pulp, and for resin, and other 

 substances. 



Pulp cells. 



De Candolle thinks, that gum, which is chemically 

 composed of oxygen, hydrogen, and carbon, is the 

 ultimate form of the pulp stored up; and by slight 

 modifications this gum takes the form of fecula, sugar, 

 and lignine 2 , or woody fibre. 



ORGANS OF AERATION. 



THOUGH plants have no organs analogous to lungs 

 or gills, nor even, I think, to the air pipes of insects, 

 to which the spiral vessels have been mistakenly, 

 it should seem, compared ; yet they cannot live with- 

 out air any more than animals, and they die when 

 deprived of it. The air being thus indispensable to 

 vegetable life, must act on the plant in some manner, 

 and experiments have accordingly proved that the 



() In French, Clostre. 



(2) This will be explained in the ALPHABET OF ORGANIC 

 CHEMISTRY. 



