66 



plant being in striking contrast in this respect to the CoviUea tri- 

 dentata examined above. 



Another interesting point is that the Teachings of the air-dried 

 leaves and blossoms mnst have contained about three times as much 

 sodium as was necessarj^ to balance the hydrochloric and sulphuric 

 acids present in the plant. The total amount of sodium calculated 

 from the ash analysis Avould be 8.32 per cent. A direct determination 

 of the sodium made on an aliquot i^art of the leachings gave 8.55 per 

 cent, while the amount calculated as necessar}^ to balance the hydro- 

 chloric and sulphuric acids, as determined by the ash analj^sis, is 2.68 

 per cent. The residue after leaching contained practically no chlo- 

 rine, sulphates, or carbonates. It would appear that in the burning 

 of the plant or in its decay the sodium, which is probably present in 

 organic combination, yields sodium carbonate as a decomposition xDrod- 

 uct, and this in turn is found in the ash or debris. It seems probable 

 that a large part of tlie chlorine which was originally taken up or at 

 least held bj' the plant in the form of sodium chloride has been thrown 

 off b}^ the plant in some manner, the sodium being retained in organic 

 combination. 



ABSORPTION OF MINERAL CONSTITUENTS BY THE PLANT. 



Inspection of the analj^ses of the ashes of plants in general, whether 

 leaves, stems, or in fact any ]3art of the plant tissues, shows that there 

 are more than enough base-forming elements to counterbalance the 

 possible inorganic acids which the results indicate to be present. 

 Moreover, the ashes are alkaline. It is still an open question as to 

 how these bases, which appear in excess, or, more generally, how all 

 the bases, are taken \\p and assimilated b}^ the plants and what 

 becomes of the acid radicals. While it is possible that some of the 

 alkaline materials may have been absorbed by the plant in the form 

 of carbonates as such, the amount thus absorbed will be relatively 

 very little, for hy obvious metathetical reactions or double decomposi- 

 tions there would be formed carbonates of the alkaline metals. These 

 latter would be hydrolized in water to some extent, giving caustic 

 solutions which would undoubtedl}^ corrode the tissues of the plants. 

 The question as to the disposition of the acid residues is then perti- 

 nent. Several possible exx^lanations suggest themselves, which seem 

 worthy of attention in this connection. 



It is possible that chlorine, for example, Avhich may have been in 

 the acid radical, has been changed by the plant in such a way as 

 to form organic substances, and that these organic substances may 

 be exhaled by the plant as odors or exuded by the leaves or roots. 

 Against the latter suggestion the exj)eriments of Diets ^ indicate that 

 the excretion of such substances by the roots is very improbable. On 

 the other hand, the chlorine or sulphur ma}^ be retained in the plant 

 tissues in organic combination in such form that they more or less 



1 Jahrb. flir wiss. Botanique, 32, 316 (1898). 



