THE GREEN-HOUSE. 



143 



greenth of leaves, brilliant-coloured blossoms and 

 fruits, as light which has not passed through glass. 

 But as all plants in green-houses can only enjoy their 

 light, or at least a great portion of it, by receiving it 

 through glass, hence the necessity of choosing the 

 very best glass — that which is clearest and has fewest 

 inequalities of surface, in order that the light may 

 pass through it as little changed as possible. Ex- 

 perience proves that the rays of light after passing 

 through glass are considerably more decomposed, or 

 at all events much more unfavourable to vegetation, 

 the distance of a yard or two from the glass, than 

 close to its surface. Hence the great importance of 

 placing plants near the glass. 



Light being required for bringing the leaves of 

 plants to perfection, it follows that plants which grow 

 all the year, as some Gemniacece, must require 

 abundance of light all the year ; but that others which 

 grow only once a year, as camellias and oranges, may 

 pass a part of the year with less light than when they 

 are in a growing state. Nature acts in conformity 

 to this law, and generally produces the growth of 

 plants at a season of the year when most light is af- 

 forded for maturation. There are a few plants which 

 grow perpetually ; but these are chiefly natives of the 

 tropics, where the light is nearly equal through the 

 year. The practical conclusion to be drawn from 

 these remarks is, that such green-house plants as are 

 in a growing state should, as far as is consistent with 

 other arrangements, be placed nearest the light ; and 



