39 



and progressively less on the soils with 18 per cent and 35 per cent 

 of CaCOj, and the Hme content of bush beans was practically the same 

 on all the soils. Thus with regard to the amount of Ume absorbed, 

 pineapples behaved similar to vetch as observed by Lemmermann 

 (see p. 11), sunflowers behaved similar to oats and buckwheat as 

 observed by Meyer (see p. 12), and bush beans behaved similar to 

 clover as observed by Lemmermann. 



The individual manner in which the different plants behaved with 

 respect to their growth and ash composition on the calcareous soOs 

 is doubtless due to individual dift'erences m the constitution and 

 physiology of the roots. Suice Dyer ' found that the cell saps of 

 various roots difi'ered in their acidity, difi'erences in the assimilative 

 power of various plants for soil constituents have often been attributed 

 to diflerences in the strength of the acids excreted by the roots of the 

 various plants. But because the cell sap is acid it does not necessarily 

 follow that the roots excrete an acid. Moreover, the only root 

 excretion that has been well estabhshed is carbon dioxid. Therefore 

 it does not seem justifiable to attribute the different behavior of the 

 various plants on the calcareous soil to differences m the acid excre- 

 tions of their roots. In the Hglit of recent investigations on the 

 permeabihty of the membrane of plant cells it seems more probable 

 that the differences observed were due to differences in the nature 

 or reactions of the cell membrane. 



It appears that the diminished growth of some of the jilants on the 

 calcareous soil is due to modifications induced in their ash composition 

 by the carbonate of hme. This conclusion is based on two general 

 assumptions, first, that ash analyses show differences in the mineral 

 nutrition of plants, and, second, that the plants which have made the 

 better growth have an ash composition more nearly approaching^ 

 the optimum. Before detailing the modifications in ash composition 

 that appear to have induced the injury in the plant, these two 

 sources of doubt in the conclusion wiU be considered. 



In the first place, it should be remembered that an ash analysis 

 does not give a moving picture of the ash composition of the plant 

 during growth, but gives a picture of the ash composition at one 

 stage of growth only. As the percentages of the elements in a plant 

 vaiy considerably according to the stage of development of the plant, 

 the complete picture of any one ash constituent would be repre- 

 sented by a curve. But an ash analysis gives ordy one point on the 

 curve, so we are really comi>ariug similar curves by points. The 

 ash analyses show differences in the muieral nutrition of the plants 

 if the points compared occupy the same relative position on the 

 curves; that is, if the plants were analyzed at the same stage of 

 maturity. As precautions were taken concerning the maturity of 



1 Dyer, B., Jour. Chem. Soc. (London), 65 (1894), p. US; BiedermannsCentbl. Agr. Chem., 23 (1894), p. 799. 



