HOUSE PLANTS. 89 



tppeurance shows that the plant has been in impure air or other- 

 wise improperly treated. Sulphur or camphor will effectually 

 remove this mildew ; and a scaly insect of the coccus tribe, which 

 appears occasionally on oranges, camellias, and similai plants, 

 may be removed by a sponge and water. 



Many persons have a dislike to plants in houses as being un- 

 healthy ; and as this dislike is in a great measure groundless, we 

 may notice it. Dr. Priestley was the first to show that the leaves 

 of plants absorb carbonic acid gas by their upper surfaces, and 

 give out oxygen by their under ones, thereby tending to purify 

 the air in as far as animal life is concerned ; because carbonic acid 

 gas is pernicious to animals, and oxygen is what that life acquires. 

 It is in the light, however, that these operations are carried on ; 

 for in the dark, plants give out carbon ; and this may be one 

 reason why plants grown in the dark have little or no charcoal in 

 their substance. It does not appear, however, that any of the 

 scentless products given out by plants are injurious to human 

 beings ; because those who live among accumulated plants are 

 not less healthy than others ; though many persons feel dislike 

 and even pain from the odors of particular plants, in a way not 

 very easily accounted for. 



On the Continent in general, and in France and Germany in 

 particular, flowers of all sorts, but particularly the most fragrant, 

 are admitted into the saloons, chambers, and even bed rooms of 

 , people of all classes ; and they, rather than complain of any ill 

 affects arising from their presence, complain more of the difficulty 

 of procuring them in sufficient abundance. The flowers most in 

 demand for the chambers of the French and Germans are, oranges, 

 jasmine, carnations, honey-suckle, mignonette, olive, rocket, rose, 

 violet, wall-flower, rosemary, stock, lavender, savory, oleander, 

 hyacinth, lilac, syringa, heliotrope, narcissus, <fec., all sweet-smell- 



