HOUSE PLANTS. 79 



air than plants which have the leaves small or of delicate texture. 

 Some tribes, as the heaths, the Epacridece, and the whole race of 

 pinnate leaved and papilionaceous flowered plants, are wholly 

 unfit for house culture. 



TREATMENT OF HOUSE PLANTS. 



Water, heat, air, and light, are the four essential stimulants to 

 plants ; water, heat, and air, to promote growth ; and light to 

 render that growth perfect. 



Water, heat, and air, man can command at his pleasure by 

 artificial means ; but over light, as an element of the perfect 

 growth of plants, we have less control. To be beneficial to plants, 

 light must come directly from the sun ; and therefore the plants 

 should be so placed, as that it may act upon them with as little 

 as possible of that refraction and decomposition which it suffers 

 when it passes obliquely through glass, or any other medium 

 except the air. Plants grown in the open air, and with such free 

 exposure to the light as their habits require, not only develop all 

 their parts in their proper form, but their leaves, flowers, and 

 fruits, have their natural colors, odors, and flavors. Plants ex- 

 cluded from light have not their natural color, odor, nor flavor, 

 they make little or no charcoal in the woody part, the leaves are 

 not green, and if they do flower and fruit, which is rarely the 

 case, the flowers are pale and scentless, and the fruit is insipid. 

 This has been proved by many experiments, of which the blanch- 

 ing of celery and endive by earthing up, and that of a cabbage 

 by the natural process of hearting, are familiar instances. A 

 geranium placed in a dark room becomes first pale, then spotted, 

 and ultimately white ; and if brought to the light it again ac- 

 quires its color 



If plants kept in the dark are exposed to the action of hydrogen 

 gas, they retain their green color, though how this gas acts ha* 



