44 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



sonous properties decrease rapidly." Phanerogams also sire easily 

 attacked by oxalates. When placed in a 2 per cent solution of neutral 

 potassium oxalate, the nucleus of an onion shows a contraction of 

 about one-fifth of its normal diameter within ten to fifteen minutes. 

 Leaves of Elodea canadensis and Vallisneria spiralis were killed com- 

 pletely in thirty-six hours'' in a 1 per cent solution. The control 

 experiments with potassium tartrate or sulphate, failed in all cases to 

 show similar action. The claim, therefore, that lime salts are neces- 

 sary to precipitate tartaric acid in plants that contain tartrates instead 

 of oxalates has no support, since neutral tartrates are not poisonous, 

 as are neutral oxalates. 



The cytoplasm succumbs last, and its death is probably a secondary 

 effect, due to the death of the nucleus and the chlorophyll body. 

 Indeed, it can be easily seen that the cytoplasm dies sooner when the 

 number of chlorophyll bodies contained in it is increased. It is on 

 this account that the circulation of the cytoplasm lasts much longer in 

 the root hairs of Ohara when under the influence of a dilute solution 

 (0.5 per cent) of potassium oxalate than it does in the cells of the 

 internodes tilled with chlorophyll bodies. An equally dilute solution 

 of neutral potassium tartrate shows no injurious action in the same 

 length of time. The writer's explanation of tin 1 poisonous action is 

 as follows: Judging from the most characteristic properties of soluble 

 oxalates, that of precipitating lime from even highly diluted solutions 

 of lime salts and that of depriving lime compounds generally of (heir 

 lime, converting it into the insoluble oxalate, lie inferred from the 

 peculiar poisonous action tfte existence of calcium-protein compounds 

 in the organized particles from which the nucleus and the chlorophyll 

 bodies are built up. Such organized calcium compounds would have 

 a well-defined capacity for imbibition, which would change with 

 the replacement of the calcium by another element, and this altered 

 water content must lead to a disturbance in the structure, which 

 must prove fatal if not remedied in its initial stages. A peculiarity 

 of protoplasm is that alteration of the structure is soon followed 

 by the chemical change from the active state of its proteids to the 

 passive. Now, when potassium oxalate acts on the inferred calcium- 

 protein compounds they yield in addition to calcium oxalate the 

 corresponding potassium-protein compounds, which, on account of 

 the different capacity for imbibition, can not physiologically replace 

 the calcium compound. Moreover, neither tartrate nor sulphate 

 (which act much less energetically than the oxalate on calcium com- 

 pounds) attacks the nucleus or the chlorophyll bodies. This also 



"This, however, is not the case with free oxalic acid. 



''There are some remarkable cases in which monopotassium oxalate exists in the 

 cell sap and still produces no injury, as, for instance, in Rumex and Oxalis. In these 

 cases it is necessary to assume an unusual density of the tonoplasts — that is, a density 

 sufficient to protect the nucleus and protoplasm. 



' ( ialcium tartrate dissolves in about 2,000 parts of water. 



