FLOWEKS AND FRUIT. 273 



and hydrogen, under the influence of light in the 

 leaves. 



715. Thus, whilst the leaves are continually adding 

 new matter to a plant, the fruit, on the other hand, 

 by absorbing that matter, checks the growth. Hence, 

 also, the practice of pruning fruit-trees with a view 

 to improve the fruit ; the young fruit thus gets an 

 additional supply of organic matter, which would 

 otherwise have gone to the formation of fresh leaves 

 had not the branches been removed. It must not, 

 however, be supposed that the formation of flowers 

 and seeds is similar to the formation of woody fibre, 

 or leaves; very diff'erent changes take place, but the 

 same general conditions are required by plants in 

 both cases. 



716. Flowers do not, like leaves, possess the power 

 of decomposing carbonic acid under the influence of 

 light; on the contrary, flowers appear at all times to 

 give out carbonic acid. From this it is evident, that 

 they must consist principally of substances containing 

 in proportion less carbon than the ordinary proximate 

 principles, such as gum and lignin. There is a com- 

 mon belief that plants in blossom deteriorate the air, 

 and, therefore, that their presence in bedrooms is 

 highly objectionable. It is true that flowers gene- 

 rate carbonic acid ; but it is probable that the evil 

 efi"ects occasionally produced by flowers in sleeping- 

 rooms, are occasioned by a minute quantity of volatile 

 oil, to the presence of which the smell of flowers is 

 to be attributed; and many of which, even in very 



