Relation to Deleterious Chemical Agents 461 



N N 



four or five dilutions between and ; while with 



10000 300000 



N N 



H 2 SO 4 prepare dilutions ranging from to 



800 8000 



Effect of insoluble particles. After following carefully the 

 discussion in the text, determine, through cultures in tumblers, 

 the concentration of CuSO* and of H 2 SO 2 which will inhibit and 

 permit growth in (1) granulated quartz or infertile sand, and in 

 (2) a rich garden loam. In these experiments use, in each case, 

 sufficient of the solution to moisten the substratum approxi- 

 mately, and in comparative experiments the same amount of 

 solution should be used. Permit the experiments to run only 

 one week, and watering will not be required. 



Toxic agents and foliage. With a hand spray or atomizer 

 treat the foliage of convenient plants in the greenhouse or field 

 with 3 per cent copper sulfate, and 5 per cent iron sulfate. 

 Study the comparative effects. Cereals, grasses, carnations, 

 and onions may be taken as types of foliage not easily wetted, 

 while dandelions, mustard, beans, and peaches will furnish suit- 

 able contrasts. 



REFERENCES 



BOLLEY, H. L. Weed Control by Means of Chemical Sprays. 



N. Dak. Agl. Exp. Sta. Bui. 80 : 541-574, pi. 11-29, 



1908. 

 BROWN, A. J. The Selective Permeability of the Covering of the 



Seeds of Hordeum vulgare. Proe. Roy. Soc. 81 B : 82-93, 



1909. 

 CLARK, J. F. On the Toxic Effect of Deleterious Agents on the 



Germination and Development of Certain Filamentous 



Fungi. Bot. Gaz. 28 : 289-327, 378-404, 1899. 

 CROCKER, W., and KNIGHT, L. I. Effects of Illuminating Gas and 



Ethylene upon Flowering Carnations. Bot. Gaz. 46 : 259- 



276, 1908. [Compare also, Knight, Rose, and Crocker, 



Science, N. S. 31 : 635-636.] 



