328 BOTANICAL GAZETTE [OCTOBER 
diseases are scarcely to be found. The general conclusion is that the small 
part which fungi play in the plant diseases of the tropics is not due to the 
absence of fungi, but the tropical conditions that influence the hosts in their 
relation to parasites.—J. M. C 
Soil acidity —DAIKUHARA” finds that more than 75 per cent of the soils 
of Japan and Korea are acid, while the Chinese, South Oceanic, and European 
soils show little or no acid. This is due to the difference in geological forma- 
tions, climatic conditions, and fertilization methods. Soils of acid rock origin 
show the most prevalent acidity, those of basic origin less, and those of laval 
ash are generally free from acids. Mesozoic formations are most commonly 
acid; tertiary, paleozoic, and diluvial next; and alluvial formations least. 
The condition in Japan and Korea is related to the common occurrence of 
acid soils in the United States. The author finds that more than half of the 
cases of acidity are due to aluminium and iron compounds of acid reaction 
that are adsorbed by the colloids of the soil and set free upon the addition of 
such fertilizer salts as KCl, K.SO,, KNO;, and NaCl. In these soils ferti- 
lizing with neutral salts alone often proves very detrimental, but fertilizing 
already known that negative colloids of the soil often render lime-poor soils 
acid by adsorbing the basic ion of neutral salts and setting free the acid. The 
author speaks of his finding as a newly discovered source of soil acidity. He 
has developed a test for soil acidity that shows advantages over the litmus, 
Baumann and Gully, or the Loew tests. He has also evolved a method for the 
quantitative determination of soil acidity. The acid soils generally bear little 
lime, and the lime factor is unfavorable, owing to the excess of magnesium 
We are now coming to recognize that many acid-forming processes “takes 
a part in the dissolution of lime from the soil and the final rendering of it acid. 
The two absorption processes described above are only two of the several 
known."—WILLIAM CROCKER 
Field physiology of cotton.—Baris and Hotton” have published an 
article on analysis of agricultural yield which exemplifies the application of 
© DarkuHARA, G., Uber saure Mineralbéden. Bull. Imp. Cent. Agr. Exp. Sta. 
Japan 2:1-40. 1914. 
si * Readers will be interested i in the eon citations from American literature, in 
di J.E y an thods 
for its detection. Science N.S. 40: 491-493. ba TRoUG JE. A.,A new method for 
e determination of soil acidity. Science N.S. 4o: 246-248. 1914. Barker, J. F., 
and Cotiison, R. C., Ground limestone for acid soils. Bull. 400. Geneva Exp. Sta- 
New York. 1015. 
= Batis, W. L., and Horton, F. S., Analysis of agricultural yield. Part I. 
The spacing eee with Egyptian cotton, 1912. Phil, Trans. Roy. Soc. London 
B 206: 103-180. 1915. 
