DESIGN. 29 



2. Light. — In erecting horticultural structures of any 

 description, the first and decidedly the most important object to 

 be kept in view, is the introduction of light ; and really, though 

 this point presents itself to architects in its simplest and plainest 

 reality, it appears to be scarcely ever fally considered ; at least, 

 we are induced to conclude so, from the instances already before 

 us. It is easy for any person to satisfy himself of the wonder- 

 ful effects of light upon vegetables under artificial culture, by 

 the most familiar illustrations. When plants are placed against 

 a wall, or other opaque body, they will speedily turn the sur- 

 face of their leaves to the light, although the medium of its 

 entrance should be many yards distant. One of the principal 

 reasons why plants thrive so badly in dwelling-houses, is in 

 consequence of their being deprived of that supply of light 

 which is essential to their development. Set a plant how or 

 where you will, it will twist and turn itself in any direction for 

 the purpose of presenting its leaves to the light, or to the aper- 

 ture where it enters unobstructed. Pure air is also a most essen- 

 tial element in the economy of vegetation ; but we may safely 

 assert, after much experience, that plants under artificial culture 

 suffer far more from a deficiency of light than from a deficiency 

 of what is called pure air. The reason of this appears obvious. 

 By the latter deficiency a plant is merely deprived of its neces- 

 sary food ; but by the former deficiency the plant is entirely 

 deprived of its vegetable functions, or its energies are so en- 

 feebled as to be incapable of assimilation. We are not speaking 

 here of light merely as distinguished from darkness, for we are 

 told, upon good authority, that the luminiferous ether is radiated 

 in all directions from its grand source, viz., the sun,^'' but of 

 its properties and influence on plants when transmitted through 

 a transparent medium, such as glass. Every gardener knows 

 that plants will not only fail to thrive without much light, but 

 will not thrive unless they receive its direct influence by being 

 placed near the glass. The cause of this last fact has never 

 been satisfactorily explained. It seems probable that the glass, 



* Principles of Chemistry, by Prof. Silliman, Jr. 



/ 



