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 * and a first attempt at its 
employment was carried out by McLean in the paper a 
mentioned. 
ON THE RELATION OF CHLORINE TO PLANT GROWTH 
By W. E. TorrrneHam 
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 occurrénce 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. 8. 43: 362-363. 1916. 
