upon the Distribution of Vegetables. 175 



Others have thought that plants themselves gave birth to 

 these foreign bodies. Schrader, having sown grains of barley 

 and wheat in washed flowers of sulphur, and watered them 

 with water containing only carbonic acid, found in the plants 

 which sprung from them, silex, lime, oxide of iron, and man- 

 ganese. Moreover, he found in them more silex than in the 

 wheat which had grown in the open fields. Braconnot dis- 

 covered silex, and carbonate and phosphate both of lime and 

 iron, in the ashes of Sinapis alba, whether they had germi- 

 nated in powdered oxide of lead, or sulphur, or between 

 grains of lead, and had been watered with distilled water. 



John, in analysing some lichens, (Ramalina fraxinea, and 

 Borrera ciliaris), which had grown at the top of a fir tree, 

 standing in earth in which no traces of iron could be found, 

 discovered in them a great quantity of this metal. Neverthe- 

 less, in his finished memoir upon the nutrition of plants, he 

 proves that all the metals which exist in vegetables, have pe- 

 netrated into them in a soluble state; iron, in the form of sul- 

 phate ; manganese, under that of carbonate or nitrate : and he 

 has established the fact, that nitrate of potash, which is found 

 in so many plants, disappears the moment they are placed in 

 earth where this salt does not exist. The beautiful experiment 

 of M. Lassaigne is in perfect accordance with these last-men- 

 tioned facts ; it shews that the silex and the salts which we 

 find in a plant reared in sulphur, excluded from the air, and 

 watered with distilled water, previously existed in the seeds 

 from which they sprung. Peschier has also observed that 

 cresses, watered with water containing sulphate of lime in a 

 state of solution, produced, when analysed, much more sul- 

 phate of potash than those which had been supplied with pure 

 water : which proves that plants can modify, but not produce 

 the chemical substances existing in their tissues. 



The last researches on this subject we owe to M. Ch. Dau- 

 beny. He has raised plants in pulverised sulphate of stron- 

 tian ; others he watered with a solution of nitrate of strontian; 

 and he has found traces of this salt only in the root, never in 

 the parts exposed to the air. On the contrary, they contain- 

 ed lime and silex, and these in more perceptible quantities 

 when they had grown in pulverised Carrara marble, than when 

 they had vegetated in quartzose sand. The existence of ex- 

 cretions from the roots, already pointed out by Murray, Hales, 

 John, Mirbel and Brugmans, has been apparently placed be- 

 yond doubt by M. Macaire. He plunged different plants in 

 water, after having carefully washed them, and found that the 

 roots of the Cichoracece secreted a juice analogous to thridace, 

 {lactiicarium) ; those of the Euphorbiacece, a gum-resinous 



