112 



HISTORY OF THE VEGETABLE KINGDOM. 



above manner plants of the horse-chestnut and 

 ahnond to some considerable size, and an oak 

 till it was eight years old. And though he in- 

 fovms lis that they died at last only from neglect 

 of watering; yet it seems extremely doubtful 

 whether they would have continued to vegetate 

 much longer even if they had been watered ever 

 so regularly ; for he admits, in the first place, that 

 they made less and less progress every year, and 

 in the second place, that their roots were found 

 to be in a very bad state. 



But if they had even continued to vegetate, 

 still the experiments were insufficient to decide 

 the point in question. Their insufficiency was 

 first pointed out by Bergman in 1773, who 

 showed, from the experiments of MargrafF, that 

 in one pound of rain water there is contained 

 one grain of earth. Eai'th, therefore, must have 

 been absorbed along with the water, so that 

 even the boasted experiment of Van llelmont, on 

 which so much stress had been laid, amounted 

 to nothing. For the rain-water employed in 

 the experiment must have contained in it as 

 much eax-tli as could have been well expected to 

 exist in the wiUow at the end of five yeai-s. 

 And if not, then it is easy to point out an addi- 

 tional source of supply ; for it has been shown 

 by Hales and others, that unglazed earthen 

 vessels when placed in the earth, wiU readily 

 absorb moisture ; so that, according to Mr Kir- 

 wan's remark, the earthen vessel in which the 

 willow was planted must have absorbed moisture 

 from the surrounding soil, impregnated with 

 whatever substances the earth contained. The 

 access of earth, therefore, is accounted for with- 

 out the joint efforts of the water and vital energy 

 of the plant, and no satisfactory proof alleged of 

 the similar formation of other substances. 



The subject was afterwards investigated by 

 Ilassenfratz, who saw the insufficiency of the 

 foregoing proofs, and objected to them because 

 no account was given of the proportions of car- 

 bon at tlie commencement and termination of 

 the respective experiments. Did not the carbon 

 of the plant increase also as well as its other 

 ingredients ? And yet the carbon could not be 

 supposed to be fonned from the water. To 

 clear up this point he analyzed the bulbs of the 

 hyacinth, and of several other plants, together 

 with a number of kidney-beans, and cress-seeds, 

 with a view to discover the quantity of carbon 

 they contained, and consequently by calculation 

 the quantity contained in any given weiglit of 

 simUar bulbs or seeds. He then made a number 

 of each to vegetate in pure water, some within 

 doors, and others in the open air, having finet 

 ascertained their weight. They gcnninated, 

 grew up, and flowered ; but produced no seed. 

 They were afterwards gathered, leaves and all, 

 and subjected to a chemical analysis, the result 

 of which was, that the carbon contained in each 



was somewhat less than the quantity which 

 existed in the bulb or seed from which the plant 

 had sprung. 



From these circumstances Ilassenfratz came 

 to the conclusion that water was not the sole 

 food of plants, because plants gi'owing in pure 

 water receive no increase of carbon, and in con- 

 sequence, without a sufficiency of this substance, 

 cannot produce perfect seeds. Not reckoning 

 the experiments of Uassenfratz conclusive, how- 

 ever, Saussure instituted others. Having gathered 

 some plants of mint {metUha piperita), he found 

 that 100 parts iu weight of the green vegetable 

 substance were reduced by drying to 40.29, 

 which were found by experiment to contain 

 10.9G of charcoal. He then took a number of 

 plants of the same species, and placed them by 

 the roots in bottles filled with distilled water ; 

 exposing them to the sun on the outside of a 

 window, but sheltering them from the rain. 

 After ten weeks of vegetation the 100 parts of 

 mint weighed in their gi-een state 21G parts, 

 which were reduced by drying to 62. They 

 had augmented therefore, in dried vegetable 

 matter 21.71 parts; but thoy had augmented 

 also in their quantity of carbon; for the 62 parts 

 of dried vegetable substance furnished 15.78 of 

 charcoal. A similar result was obtained from a 

 similar experiment upon beans, from which we 

 may infer the accuracy of Saussure, and the con- 

 sequent inaccuracy of Hassenfratz, who was no 

 doubt misled by some circumstances not taken 

 into the account. Perhaps, the plants on which 

 he made his experiments were not sufficiently 

 exposed to the light of the sun; so that if ho 

 connected one error he committed also another. 

 While it is maintained, therefore, that water is 

 not the sole food of plants, and is not convertible 

 into the whole of the ingi'cdients of the vegetable 

 substance, even with the aid of the vital energy, 

 it must, at the same time, be admitted that 

 plants, though vegetating merely in water, do 

 yet augment the quantity of their carbon. 



Gases. When it was found that water is in- 

 sufficient to constitute the sole food of plants, 

 recourse was next had to thn assistance of the 

 atmospheric air, and it was believed tliat the 

 vital energy of the plant is at least capable of 

 furnishing all the different ingredients of the 

 vegetable substance, by means of decomposing 

 and combining, in different ways, atmospheric 

 air and water. But as this extravagant con- 

 jecture is founded on no proof, it is consequently 

 of no value. It must be confessed, however, 

 that atmospheric air is indispensably necessary 

 to the health and vigour of the plant, as may be 

 seen by looking at the different aspects of plants 

 exposed to a free circulation of air, and plants 

 deprived of it; the former are vigorous and 

 luxuriant, the latter weak and stunted. It may 

 be seen also l)y means of experiments even upon 



