415] W. E. Tottingham 217 



the effective climatic conditions. This general method for 

 the comparative study of climatic conditions has been sug- 

 gested by Livingston and McLean 3 and a first attempt at its 

 employment was carried out by McLean in the paper already 

 mentioned. 



ON THE RELATION OF CHLORINE TO PLANT GROWTH 



By W. E. TOTTINGHAM 



As a result of experiments conducted early in the develop- 

 ment of the water-culture method, chlorine has been con- 

 sidered as one of the unessential elements for the growth of 

 plants in general. Nevertheless, all seeds contain more or 

 less of this element and in no instance has a plant been limit- 

 ed to this original source of chlorine through successive gen- 

 erations, so that it may still be said that the question here 

 raised has never been really tested. Practically all soils con- 

 tain considerable amounts of chlorine in the form of chlorides 

 and its occurrence in plants appears to be confined to this 

 form. That this element may have important effects under 

 some conditions, when applied as an agricultural fertilizer, 

 is indicated by a common practice in some parts of Europe, 

 of adding common salt to stimulate the growth of mangel- 

 wurzel and of mixed meadow grasses, but the manner in which 

 this effect is produced has not been made clear. It has been 

 observed that unrestricted application of chlorides may lead 

 to poisoning of the soil, and agriculturists have been advised 

 specially against the use of potassium chloride as a source of 

 potassium for tobacco, the potato and the sugar beet. Euro- 

 pean investigators have reported a decreased content of starch 

 in the potato tuber as a result of the substitution of this salt 

 for potassium sulphate. 



3 Livingston, B. E., and McLean, F. T., "A living climatological 

 instrument." Science, n. s. 43: 362-363. 1916. 



