250 THE FLORIST AND 



Soil that is properly aerated, deeply trenched, and judiciously manured, 

 will support a luxuriant growth, no matter how long a dry spell we may 

 have, more especially if the surface is kept loose and open, to prevent, in 

 some degree, evaporation of moisture, and radiation of heat. 



Wm. Saunders. 

 [In G-ermantown Telegraph. 



AERATION AND VENTILATION. 



There are many who will scarcely give themselves the trouble to inquire 

 in what respect aeration differs from ventilation, and in consequence of not 

 doing so, regard the two as synonymous. Indeed, I may almost say, this is 

 generally the case, although on a little reflection it must be evident they 

 are not identical, as was shown when they were formerly noticed in the 

 Gardeners' Chronicle. In the volume for 1845, p. 267, aeration is defined 

 as " the art of keeping the atmosphere of a forcing house in motion by 

 currents of warmed fresh air," whilst ventilation is stated to mean " the 

 process of letting the external air at once into the forcing house." This is 

 no fine drawn distinction, but a very important difference which every culti- 

 vator ought to bear in mind, especially when it is considered that it is 

 mainly owing to the power they possess of regulating the atmosphere of 

 their forcing houses in a proper manner, and at the time required, that 

 their success is to be attributed. The reason why aeration is advantageous, 

 has been so clearly pointed out and explained in the article to which I have 

 just referred, that I trust I shall be excused for bringing it again under the 

 notice of those who are likely to profit by its study and perusal. It is 

 there stated that — "A man's reason must tell him that a plant condemned 

 to pass its life in a still atmosphere, is like nothing so much as a criminal 

 set fast in an everlasting pillory. In order to secure motion in the vege- 

 table kingdom, currents of air are made to do the work of the muscles, 

 limbs and volition of animals. It' is not at all improbable that, in addition 

 to the mechanical effect of motion in assisting the propulsion of the sap, it 

 may be important that the stratum of air in contact with the leaves of 

 plants should be incessantly shifted, in order to enable them to procure an 

 adequate supply of food ; for we find that water in motion feeds them better 

 than that which is stagnant. Leaves are continually abstracting from the 

 air the very minute quantities of carbonic acid which it contains. When 

 the air moves quickly over the surface, fresh supplies of that food are in- 



