468 



ACTION OF THE SALTS OF IRON ON VEGETATION. 



of oro^anic mnladies peculiar to tlie indi- 

 vidual plant, which socni to be, in general, 

 inherent to the individual structure, and are, 

 like it, multiplied by grafts and cuttings, 



" These plants are not affected by the 

 temporary changes of an undoubted disease, 

 and the term chlorosis, and the experiments 

 of M. Gris, are in no way applicable to 

 them ; their pale or yellow stripes derived 

 no change from the action of the Salts of 

 Iron. 



" The chlorotic plants, on the contrary, 

 cultivated in pots, and watered with a solu- 

 tion of the sulphate of iron, containing from 

 2.\ to 5 drams of this salt to a quart of wa- 

 ter, have, in almost every instance, after 

 two, three or four waterings, gradually re- 

 covered their natural green color, the quan- 

 tity of solution ajjplied to each one varying 

 from half a gill to a pint, according to the 

 size of the pot in which the plant is culti- 

 vated, and the strength of the plant itself; 

 but the effect has been more or less prompt 

 and more or less marked according to the 

 nature of the plant. 



" Thus a very sickly cMorroiiz Geranium, 

 conjointly with a Calceolaria ezcelsa, Stachys 

 moUissima and Malva capensis, in the same 

 condition, derived a prompt effect from three 

 waterings, and entirely recovered its color at 

 the end of three weeks ; three other plants, 

 Satureia, Diosma and Malaleuca, alike quite 

 yellow, acquired a return of natural color 

 more sluggishly, a beautiful green being 

 developed in about two months ; a Phnelea, 

 on the contrary, regained its color imper- 

 fectly, and many of its leaves still remain 

 yellow. 



" It is worthy of remark, that if the paren- 

 chyma, during the progressive functional 

 changes of the plant, becomes so attenuated 

 that the leaf is almost transparent and on 

 the point of withering, the susceptibility of 

 being made green ceases, and the favorable 

 influence of ferruginous solutions can only 

 be manifested on the new leaves that may 

 be developed. 



♦' A plant, cultivated in the open ground, 

 in the Jardin des Plants, offered a striking 

 illustration of this fact : this was a vigorous 

 bush of a Napcea levis, so diseased in the 

 month of May, that its whitish-yellow, thin, 

 and almost transparent leaves, were partly 



crisped and desiccated, and its buds were 

 as while as the centre of a cultivated k'ttu<-e ; 

 a solution of nearly one dram of sulphate of 

 iron in three gills of water, twice applied, 

 sufficed to indicate a change in the color of 

 the leaves not too much withered ; a third 

 and more liberal watering restored vigor 

 and natural color to most of the shoots ; but 

 this (juantity was not sufficient to affect per- 

 manently so large a bush, presenting more 

 than thirty branches, so that its leaves are 

 alreadjf becoming marbled with yellow. 



"Plants in the open ground are not fa- 

 vorably situated to offer uniformhj certain 

 results ; the absorption by the roots being 

 far from satisfactory, which may be partly 

 attributable to the extension of their roots, 

 and partly to the imperfect absorption of the 

 liquid, which becomes diffused, and conse- 

 quently enfeebled. 



" It is probable, when the necessary pro- 

 portions are understood, especially for pe- 

 rennial plants formed with vigorous heads, 

 that the same conclusions will be reached 

 as from plants in pots. 



"We should not, indeed, question the 

 action of the solutions of sulphate of iron, 

 when applied to chlorotic plants ; but does 

 the sulphate of iron act directly, as a ferru- 

 ginous salt, or, re-acting on the substances 

 which compose the soil, does it produce its 

 effect as a sulphate of lime ? This objection 

 has been urged to M. Gkis, and he has 

 sought to answer it by various experiments. 

 He affirms that he has obtained like results 

 from solutions of the chlorate and of the 

 nitrate of iron, while the sulphate of lime, 

 on the contrary, effected no change in the 

 color of chlorotic plants. 



" Many of the plants tried by him, and 

 many of those also submitted to the expe- 

 riments of your commissioners, were culti- 

 vated in pure peat-earth, (terre de bruyere 

 pure,) and the most signal results were ob- 

 served, although the soil was almost entire- 

 ly free from calcareous matter. 



"Finally, the application of the ferru- 

 ginous solutions directly to the chlorotic 

 leaves themselves, by bathing, seems to re- 

 solve every doubt as to their positive action 

 on the tissue of the leaf. 



" This process, which M. Gris practiced 

 subsequent to that of absorption by the roots, 



