18097 | CURRENT LITERATURE 225 
be assimilated. All other cells of the plant must use as food such substances 
as sugar, asparagin and amides from which to construct cellulose, starch and 
protoplasm. 
A large number of cultures were made to determine whether plants could 
use organic food. eak solutions of various acids, alcohols, aldehydes, 
ketones and amido-compounds were employed. Since free acids are always 
poisonous they were neutralized with milk of lime. Except where the com- 
pounds employed were active poisons, almost none failed to be, to some 
extent, assimilated. 
e author gives in condensed tabular form the results of his own work 
and that of other investigators. Some organic compounds can be used only 
in presence of light and assimilation is aided by light in all cases. Such sub- 
stances as peptone, glycerin, asparagin and sugar in which fungi grow luxu- 
riantly are also suitable as food for green plants. 
Of great interest is the successful artificial culture of green plants with 
amido compounds such as asparagin, leucin, tyrosin, glycocol, etc., since 
these products of proteid decomposition are often present naturally in the 
soil, It has been definitely shown that asparagin can furnish nitrogen for 
the formation of proteids and in some cases plants thrive better if provided 
in this way than when obliged to obtain nitrogen from nitrates of the alkali 
metals. 
The significance of the use by plants of organic matter is not to be under- 
rated. Plants thrive better when furnished with such food. Decomposition 
products are taken up by plants and thus removed from the soil. Rivers, 
polluted with sewage, undergo, by means of the vegetation they contain, a 
continual self purification. 
Many carbon compounds can be assimilated by green plants in the dark. 
A preliminary splitting of the molecule into CO, and H,O does not occur, for 
the assimilation of CO, takes place only in the light. The author is inclined 
to agree with the ppathicsis of O. Loew that from all organic substances used 
as food the molecular group CHOH is produced, and either with the aid of 
ammonia proteids are formed, or without such assistance carbohydrates are 
developed. In support of this theory he adduces the fact, proven by experi- 
ment, that such compounds as contain the group CHOH ready made are 
most readily assimilated. Further investigation on this point is very much 
needed.— FRANCIS RAMALEY, University of Minnesota. 
