IMPORTANCE OP FREE AIR. ^01 



example, the (Enanthe erocata, whose leaves and roots are 

 poisonous in the midland counties of England, is innoxious 

 in the lower temperature and cloudier sky of Edinburgh; no 

 art can induce the Khuharb plant to form in Europe the 

 medicinal substances which give value to the drug in those 

 bright, and heated regions of Asia which it inhabits ; nor can the 

 Tomatoes or Aubergines ripened in England be for a moment 

 compared for excellence to those produced in the North of 

 Africa. 



It must however be observed, that the effect of heat and 

 light is greatly increased by free exposure to currents of air, 

 such as are incessantly acting upon the surface of plants in the 

 open ground. Whether this results from the greater abstraction 

 of moisture, or from a more abundant supply of gaseous food to 

 be absorbed from the atmosphere, or from any unknown 

 circumstance, it is certain that all vegetable secretions, of 

 whatever kind, are improved in quahty when air has the fullest 

 access to the plants. Of this we have abundant proof when we 

 contrast the pallid, subacid Pine-apples of forcing houses, with 

 those ripened out of doors as has been practised in the garden 

 of the Baroness Kolfe at Bicton; or when we compare the 

 brilliant colours and rich perfume of flowers and fruit formed 

 in thoroughly ventilated hothouses, with the same productions 

 taken from glass houses to which the air has very little access. 



The following is tte maimer ia whicli tHe Pine-apples above alluded to 

 were grown at Bicton. 



In May Mr. Barnes, having some plants ready, opened a trench, casting^ 

 the earth right and left, so as to form a hank on each side, which would 

 afford shelter from cold winds; in the bottom of the trench he placed 

 bricks in threes, in the form of a triangle, so as to make a dry bottom 

 for the plants to stand on, and at the same time to secure a ready 

 passage for air and water. The plants having been placed on the 

 bricks, Were packed to the rims of the pots in leaves which had been 

 used during the winter. This being done, the whole surface, banks and 

 all, was covered with charredhnj or grass, for the purpose of absorbiug 

 heat, retaining it, and giving it off gradually. Although the weather 

 proved cold, with frosty mornings, and many sunless days, yet no 

 injury was sustained, and when the sun did appear the fruit made 

 great progress ; at the same time the suckers which sprung up grew 

 vigorously and were most healthy. The varieties employed consisted 



