270 



BOTANICAL GAZETTE 



[OCTOBER 



in the solution. Absorbent cotton was packed in the neck of the 

 bottle to exclude dirt and hinder evaporation. The results were 

 similar to those described above, as will be seen from Table VIII. 



Finally the question was raised whether 

 the tissues of the stem and leaf, if brought 

 into direct contact with the solution, would 



behave like the root. To 

 answer this, sections of 

 considerable (but uni- 

 form) thickness were cut 

 with a microtome and 

 placed in the solutions. 

 The results appear in 



Table IX. 



The results described 

 in this paper are in all 



striking 



m 



essentials 

 agreement with those 

 obtained from the study 

 of marine plants, as well 

 as from the study of 

 marine and fresh-water 

 animals as referred to in 

 the first part of this 



paper 



This agreement 



360m 



2, in distilled 



water, aggregate length of roots 740^™. 



Fig. 7.— Growth of roots of wheat for 40 days. shoWS that the principle 

 I, in dilute artificial sea water (NaCl = ap.3m/25), ^f balanced solutions is 



of general vahdity .^ The 

 application of this prin- 

 ciple to soil and river water^ and to nutrient solutions, I hope to take 

 up in a subsequent paper. 



3 LoEw and his pupils have shown that calcium antagonizes magnesium (cf. 

 Bull. No. 18, Div. Veg. Phys. and Path. U. S. Dept. Agric. 1899). See also the antago- 

 nistic effects noted by Kearney and Cameron (Report No. 71, IT. S. Dept. Agric. 

 1902) in their studies on the salts of alkali soils. The method employed by them 

 (observation of the root-tip only) is so dififerent from mine that I have not attempted 

 to compare the results, 



4 In the first part of this paper I have referred to the composition of tap water, 

 but it seems advisable to defer the discussion of this point. 



