LIME AND TRANSPORTATION OF STARCH. 55 



has already been mentioned that a similar phenomenon was observed 

 by Nobbe in plants showing- a deficiency of chlorine compounds. Two 

 causes, either separately or combined, may produce this phenomenon, 

 and it follows, therefore, that the conditions bringing' it on in different 

 cases may not necessarily be wholly identical. One cause irmy be 

 that cells fail to produce the diastase which is necessary for dissolving 

 the starch, and another the impossibility of forming in the growing 

 parts new plastids and chloroplasts, which produce starch from sugar. 



The writer's view, according to which lime is required in the com- 

 pounds which build up nuclei and chromatophores, explains not only 

 the failure to increase these organoids, but also to produce diastase 

 when lime is absent. Enzymes are secreted from the nuclei, as Hofer 

 has shown with amoebae, and therefore if the nuclei can not be normally 

 formed for want of lime enzyme formation also may cease. However, 

 this latter explanation does not seem to apply for the initial patho- 

 logical stage, since Raumer and Kellerman observed that in Phaseolus 

 hi ultiflorus sugar also was formed from starch for a certain period when 

 lime was deficient; hence diastase was probably present. 



In this case the upper part of the stem was devoid of starch and 

 seemed to be incapable of forming starch from the sugar present. This 

 accumulation of sugar prevented any further solution of starch in the 

 lower parts. 



The intensity of starch transportation depends essentially on two 

 factors, (1) the saccharifying activity and (2) the starch-forming 

 activity of the leucoplasts in other parts of the plants. 



Further investigations in this direction w^ould be very desirable. 

 They would perhaps also show differences between the action of 

 chlorids and that of lime in regard to the transportation of starch. 

 Finally, since a deficiency of lime, like the absence of phosphoric acid, 

 potassa, or magnesia, stops the formation of new cells, an accumulation 

 of proteins may result, and indeed such a case was observed by Stock, 

 the crystalloids increasing in number when lime was deficient." 



THE PHYSIOLOGICAL ROLE OF MAGNESIUM SALTS. 



It has already been pointed out that magnesium salts are especially 

 important in the formation of seeds, but they are also required by all 

 other parts of plants, and especially in the process of development. The 

 amount of magnesia taken up by crops varies considerably. For 

 example, an average crop of wheat will take up 8 kilos per hectare, a 

 crop of leguminous plants 12 kilos, and a crop of tobacco as much as 

 43 kilos. It has also been pointed out that magnesium salts can fulfill 

 their nourishing functions only in the presence of calcium salts, while 

 in the absence of calcium salts they even exert an injurious action/' 



"Pot. Centralbl., Vol. PHI, p. S3. 



''Only the lowest algse ami fungi arc exceptions 



