268 



BOTANICAL GAZETTE 



[OCTOBER 



could be detected. The solutions were renewed from time to time and 

 the concentration ascertained by occasional titration. 



It should be said that in general the growth of 

 roots (or any parts in direct contact with the 

 solution) furnishes a much better criterion of the 

 effect of solutions than the aerial portions of the 

 plant. In certain solutions which are so poisonous 

 that the roots cannot develop, the leaves may grow 

 fairly well for a time. In these cases the poisonous 

 solutes are apparently filtered out by the tissues 

 of the seed as the solution passes through them 

 on its way to the leaf. For this reason the figures 

 for the growth of roots only are here given. The 

 results are shown in Table VII and figs. 6 and 

 7, which give the average of five series of ex- 

 periments. Each number represents average 

 measurements of at least four or five hundred 

 seeds. This is necessary in order to do away with 

 the individual variation so common in seeds. 



FIG. 5. Sectional 

 view of wall of tumb- 

 ler and seed sup- 

 ported by folded 

 filter paper; p, paper; 

 s, seed; t, tumbler; 

 w, water line. 



TABLE VII. WHEAT 

 All quantities given are cubic centimeters of 3^/25 solutions. 



CULTURE SOLUTION 



Dilute artificial sea water: 

 1000 NaCl 

 78 MgCl, 

 38 MgS0 4 

 22 KC1 

 io CaCl 2 



Distilled water. . . . 

 NaCl... 

 1000 NaCl 

 io CaCl 2 



1000 NaCl 

 22 KC1 

 io CaCl 2 ' 



1000 NaCl 

 78 MgCl a 

 io CaCl 2 

 MgCl 2 .. 

 KC1.... 

 CmCl... 



GROWTH IN 40 DAYS 



Aggregate length of roots 

 per plant in mm. 



360 



59 



254 



324 



327 



68 



70 



