EVOLUTION AND GROWTH. 33 



In the botanical gardens of Berlin, Potsdam, and Vienna, this pro- 

 perty of chlorine lias been made available to excellent ends; by its 

 means many old seeds, upon which a great variety of trials had 

 already been made in vain to make them sprout, were brought to 

 germinate. At Schoenbrunn, for instance, they had never succeeded 

 in raising the clusea rosea from the seed ; but M. de Humboldt suc- 

 ceeded at once, by forming a paste of peroxide of manganese, with 

 water and hydrochloric acid, in which he set the seeds of the clusea, 

 and then placed them in a temperature of from 62° to 75° cent. 

 (143° to 167° Fahr.) It seems very likely that this discovery of M. 

 de Humboldt may yet be taken advantage of in our every-day hus- 

 bandry. It is quite certain that the whole of the seed which we 

 commit to the ground, does not spring up, especially when we are 

 forced to have recourse to seed that is two or three years old ; the 

 loss is then frequently very considerable. But a solution of chlo- 

 rine, or a mixture which would evolve it, could not cost much, its 

 use would add little or nothing to the very trifling expense which is 

 generally incurred in pickling the wheat that is employed as seed. 



§ III.— EVOLUTION AND GROWTH OF PLANTS. 



As germination advances, we see those organs acquiring shape 

 and size which had appeared at first in the rudimentary state. The 

 roots extend in length, and increase in number, and their extremities 

 become covered with capillary fibres. The stem as it rises puts 

 forth branches in all directions, which become covered with leaves. 

 The cotyledons which had nourished the young plant during the 

 first days of its existence, wither and fall. Under the influence of 

 the solar light, the vegetation progresses amain, and the organic 

 matter, which finally constitutes the plant when it has attained matu- 

 rity, weighs vastly more than the same matter which existed pre- 

 viously in the seed. To quote a single instance from the family of 

 annual plants, a seed of field beet of the weight of ,06175 of a crrain, 

 may by the end of the autumn give birth to a root which with its 

 leaves shall weigh 162099grs. or upwards of 281bs.* 



This immense and rapid assimilation can have no other source 

 than the soil, the air, and water. Without, at this time, pausing to 

 consider the useful influence which the soil, and the substances it 

 contains, exert upon the entire development of vegetables, we shall 

 here assume it as a general principle that water and the air of the 

 atmosphere alone, are capable of furnishing them with all the ele- 

 ments which enter into their composition, to wit — carbon, hydrogen, 

 oxygen, and azote. In other words, a seed may germinate, vegetate, 

 give birth to a plant which shall attain to complete maturity, by the 



* Actual weight of a beet-root grown at Bechelbronn in 1841 



