G82 General Notices. 



have remained satisfied without purifying the sulphate of strontian in which 

 the seeds were sown, from the other earths with which I found it to be mixed. 

 But the labour of getting rid of these ingredients seemed to be uncalled for 

 with reference to the objects to which I found it necessary to confine my 

 enquiries ; since, even had I employed the earth in a state of perfect purity, 

 and detected an excess of lime in the plants reared in it beyond that con- 

 tained in their seeds, still I should not have been justified in inferring the 

 actual generation of earthy matter, any more than I have felt myself to be 

 from the similar result I obtained when flowers of sulphur were the matrix 

 in which the plants had vegetated. The faculty, however, possessed by them 

 of rejecting strontian, even when presented to the absorbing surfaces of their 

 roots in a state of solution, would seem sufficientlj' substantiated; and an 

 analogous circumstance may be cited in the animal kingdom, if I can rely 

 upon an experiment which I made several years ago, — that of confining some 

 hens of the guineafowl, during the breeding season, in a place where they 

 could obtain no other earth except some powdered sulphate of strontian, 

 which they appeared to devour greedily. Yet only a minute trace of this 

 earth was discoverable in the shells of their eggs, of which those laid during 

 the first part of their confinement retained their natural hardness ; but those 

 of later production were as soft as if the birds had been entirely debarred 

 from every kind of earthy matter. It may be asked, whether the strontian is 

 taken first into the system, and afterwards excreted from it, or whether the 

 spongioles of the roots refuse it admission? The latter supposition seems the 

 more probable one ; since, if we adopt the former, we ought to be able always 

 to find traces of the earth diffused throughout the vegetable tissue; and I 

 may relate an experiment of my own, which seems to confirm it, undertaken 

 after the plan of those by means of which the ingenious M. Macaire of Geneva 

 established his important doctrine with respect to the excretory function dis- 

 charged by the roots of plants. A small pelargonium was taken out of its 

 pot, and its roots divided into two nearly equal bundles ; one of which had its 

 extremities immersed in a glass containing a weak solution of nitrate of 

 strontian, the other in one containing pure distilled water. After a week 

 had elapsed, the water contained in the second glass was tested; but no 

 strontian could be discovered in it, though a single grain in one pint of water 

 ■would have been I'eadily detected by my method. Hence it would seem that 

 the strontian is not excreted by the roots. Yet this power of rejecting the 

 earth in question, if possessed by the plant, must be held compatible with 

 that of absorbing the water containing it, with which its roots are in contact. 

 I took out of the ground a small lilac (^Syringa vulgaris), and introduced its 

 roots into a glass globe containing seven pints of a weak solution of nitrate 

 of strontian. In about a fortnight the quantity was reduced to three pints — 

 the remainder having, for the most part, been absorbed by the roots ; for 

 evaporation was prevented by covering the surface of the water with a 

 stratum of olive oil, and the mouth of the vessel with a cork. Unluckilj^, 

 the original quantity of salt had not been estimated ; but it was found that 

 what remained in the water, at the close of the experiment, yielded 69'4 grains 

 of sulphate of strontian, equivalent to 39"2 grains of the earth. The four 

 pints of water, therefore, consumed, if they had passed through the organs of 

 the vegetable charged with their original quantity of nitrate of strontian, 

 would have carried into its circulation 22*4 grains of this earth; and, as the 

 water was absorbed at the average rate of about 4^ ounces per diem, it 

 follows that more than l^ grain would have been carried daily through 

 the substance of the plant, supposing the salt to have been taken up in 

 the same ratio as the water. Now, on burning the plant, and examining 

 its ashes, a trace of strontian certainly was detected ; but its whole amount 

 did not reach the one fifth of a grain, that is, 2 per cent of the whole 

 quantity of earthy matter present; my analysis indicating, of hme, 7*30 grains; 

 strontian, 0*18 ; total quantity of earth, 7*48. 



" The conclusion to which I have been led by the foregoing experiments may 



