134 THE ART OF CULTURE. 



in the first case a mealy, in the second a soapy, con- 

 sistence. Beet-roots taken from a barren sandy soil 

 contain a maximum of sugar, and no ammoniacal 

 salts; and the Teltowa turnip loses its mealy state in 

 a manured land, because there, all the circumstances 

 necessary for the formation of cells are united. 



An abnormal production of certain component 

 parts of plants presupposes a power and capability 

 of assimilation, to which the most powerful chemi- 

 cal action cannot be compared. The best idea of 

 it may be formed, by considering that it surpasses 

 in power the strongest galvanic battery, with which 

 we are not able to separate the oxygen from car- 

 bonic acid. The affinity of chlorine for hydrogen, 

 and its power to decompose water under the influ- 

 ence of light, and set at liberty its oxygen, cannot be 

 considered as at all equalling the power and energy 

 with which a leaf separated from a plant decom- 

 poses the carbonic acid which it absorbs. 



The common opinion that only the direct solar 

 rays can effect the decomposition of carbonic acid 

 in the leaves of plants, and that reflected or diffused 

 light does not possess this property, is wholly an 

 error, for exactly the same constituents are gene- 

 rated in a number of plants, whether the direct 

 rays of the sun fall upon them, or whether they 

 grow in the shade. They require light, and, 

 indeed, sun-light, but it is not necessary that the 

 direct rays of the sun reach them. Their functions 

 certainly proceed with greater intensity and rapidity 



