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 w^ell 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 



Fig. 5. — Sectional 



on its wav to the leaf. 



For this reason the figures 



view of wall of tumb- ^^^ the growth of roots only are here given. The 

 ler and seed sup- results are shown in Table VII and figs. 6 and 



ported by 



sup- 

 folded 

 filter paper; p^ paper; 



y, which give the average of five 



series 



of 



ex- 



w^ water line. 



5, seed; t] tumbier| perimcnts. 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. 



TABLE VII. WHEAT 



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





Growth in 40 Days 



Culture Solution 



Aggregate length of roots 

 per plant in mm. 



Dilute artificial sea water: 

 1000 NaCl \ 

 78 MgCl. ) 

 s8 MeSO. > ■. . 



K 



w 



360 

 740 



59 

 254 



324 



327 



7 



68 



22 KCl \ 



xo CaCU ' 

 Distilled water 



NaCl 



1000 NaCl if 



10 CaCla > * 



1000 NaCl ) 



22 KCl V 



10 CaCla ) 



1000 NaCl ) 

 78 MgCU f 



10 CaCla ) 



MgCla 



KCl 



CaCU 



70 





