1846.J JVheat. 133 



ground on which it grows, but that the exhaustion, which is 

 always clear when the crop is entirely taken away, becomes so 

 much the less sensible, as there remains in it a greater or less 

 quantity of residual parts. 



The slightly exhausting effect then of vegetables before flow- 

 ering, is tar Irom establishing the point that during their early 

 stage of growth they subtract but little from the soil; the above- 

 mentioned facts prove the contrary, at the same time that they 

 seem to indicate that at this epoch the plant already holds in re- 

 serve, accumulated in its organs, a large portion of the matter 

 which at a later period wmII concur in the formation of the seed. 

 We know, for example, that vegetables taken up after fecunda- 

 tion yield seed notwithstanding, when they are kept in a proper 

 state of moisture. 



When a vegetable is fecundated the reproduction of the species 

 is insured, for, stiictly speaking, it is effected under mere meteo- 

 rological influences. Proceeding from this phase of vegetable 

 lite, the matter accumulated is carried towaids the point where 

 the fruit is to be developed; the green color of the leaves gradu- 

 ally fades, the saccharine and amylaceous principles, and the 

 azotized substances, leave gradually the stems and roots. Clover 

 and Beet after having produced seeds can no longer be considered 

 as fodder, their stems and leaves presenting merely a ligneous 

 and insipid tissue. 



In consequence of this appropriation of the succulent principles 

 of the roots, we understand that a full grown plant will leave 

 only a small residual part in proportion to what it would have 

 left before maturity. It is to this diminution in the organic mat- 

 ter of the residuum, that M. de Dombasle has attributed the ex- 

 haustion occasioned by crops; but does it follow necessarily from 

 this concentration of the juices towards a single organ, that from 

 the moment it commences, the air and Atmosphere cease to have 

 any part in the phenomena of vegetation, and that the whole 

 work of organization which is accomplished after flowering is 

 formed merely at the expense of the materials stored up in the 

 tissues of the plant. This is the opinion of M. de Dombasle. 

 Nevertheless, after flowering, the leaves preserve for a long time 

 their aerial functions, and the moisture which escapes from their 

 leaves shows that the roots have not ceased their functions. 

 We see that for an ill-founded opinion, an opinion entirely con- 

 trary, but not sufliciently justified in every point of view, has been 

 substituted; it was conteniled that assimilation takes place prin- 

 cipally during fructification; M. de Dombasle affirms that a fe- 

 cundated plant incloses already all the elements necessary for 

 maturation, and as he did not find for his defence arguments as strong 

 as those which^he had employed for the attack he had recourse to 

 experiment. 



