AGRICULTURAL BOTAXY, CHEMISTRY AND PHYSIOLOGY OF PLANTS 963 



Determinations of specific gravity repeatedly carried out on speci- 

 mens of the same class (cellar-stored) proved that the divergencies between 

 the maximum and minimum values were greater in " Imperator " than 

 in " Up to date ". In the former the minimum content of starch was 13.9 % 

 and the maximum 16.6 "„. while in the latter the minimum content was 

 12.3 % and the maximum 13.9 %. Therefore the range was 2.7 % in. " Im- 

 perator " and 1.6 % in " Up to date ". The difference in the range of 

 values in these two varieties is not merely accidental, but appears to be 

 related to the fact that in " Imperator ", especial!}' in large tubers, big 

 hollows occur more frequently, and this variety is more liable to rot than 

 the other. This observation if practically applied to other varieties of 

 potatoes might have useful results. 



The variations in the specific gravity of potatoes checked by accurate 

 analyses again confirm the fact that the usual rapid method of determina- 

 tion of starch and dry substance based on an estimation of specific gravity 

 of potatoes furnishes only approximate and unreliable results. 



744 - Rapid action of Saline Solutions on Living Plants: Reversible Displacement of a 

 part of the Basic Substances contained in the plant. — devaux henry, in Comptes 



Rendiis dc V Academic dc.<: Sciences, Vol. it.::, No. 15, pp. 561-563. Paris, April 10, 1916. 



By previous studies the writer ascertained that the cell walls, and in 

 particular the pectose they contain, are able to fix energetically an ap- 

 preciable quantity of all the bases present in the form of salts.- Prolonged 

 washing in distilled water does not remove the metals thus fixed. On the 

 other hand, steeping for a short time in the solution of another metal 

 causes the immediate separation of the metal which distilled water had been 

 unable to remove. These phenomena of mutual displacements are rever- 

 sible. Just as alkaline metals can be displaced b}- all others, in particular 

 calcium, the latter can in turn be expelled by alkaline metals. 



These results at once suggested the question whether the interchanges 

 ubserved on isolated cell walls also take place in living plants. 



The question is answered by the following investigations : 



A 10 to 15 gram lot of some aquatic plant was placed in a suitable 

 vessel and carefully washed with distilled water (distillation carried out 

 in glass in order to avoid the marked traces of copper or lead frequently 

 found in commercial di.stilled water), after which, it was subjected to the 

 following steepings of 30 minutes each : i) in 250 cubic cc. of distilled water ; 

 2) after washing with distilled water, in 250 cubic cc. of i per 1000 saHne 

 solution ; 3) after careful washing with distilled water, in 250 cc. of distilled 

 water. The liquid was tested with oxalate of ammonia after each mace- 

 ration. Result : no calcium after the first and third maceration ; presence 

 of calcium after the second maceration (in saline solution). 



It follows from these experiments that a very rapid decalcifying ac- 

 tion of the plant was produced by the alkaline salts present in the solutions 

 employed. This decalcification is a general phenomenon, having been ob- 

 served by the writer in various plants (phanerogams, cryptogams, aquatic 

 roots, terrestrial plant roots, etc.) and with dift'erent salts. The decalcify- 

 ing salt may be an alkali or alkaline earth, but it may also have any acid 



