OLDENBUSCH: STIMULATION OF PLANTS a75 
cultures unexposed. Furthermore the oxalic acid formation was 
lower per unit dry weight in the stimulated cultures. 
Johannsen (16) was the first to discover that exposing dor- 
mant buds to an atmosphere impregnated with ether forced the 
buds to open earlier than normal. Chloroform has the same 
effect but is more powerful, less being needed to bring about the 
same result. 
No attempt has been made to cover the whole field of the 
very voluminous literature on this subject. A comprehensive 
account may be found in Czapek’s ‘‘ Biochemie der Pflanzen,” 
second edition, Vol. 1, page 147 et seq., 1913. 
Among the investigators who experimented with carbon 
disulphide, none used it in gaseous form but either in pure liquid 
state or in aqueous solution. Sirker (17) in Japan found that 
mulberry bushes, grown in soil previously treated with CS., pro- 
duced more branches, higher plants and more leaves with a 
greater dry weight for each individual leaf than bushes grown in 
untreated soil. Koch (18) in 1912 found the same thing with 
other plants. Koch asserts that the carbon disulphide is not 
used as a carbon source, nor does it act as an insecticide in 
killing off the harmful lower organisms in the soil, since under 
such circumstances a larger amount of the CS. would be more 
beneficial. This, however, is not the case, a larger amount of 
the CS. being harmful, and the stimulation takes place only when 
the compound is added in minute quantities. Fred (19) in the 
same year stated that carbon disulphide added to the soil in 
dilute solutions stimulated the growth of soil bacteria, the nitro- 
gen-fixing forms in particular, so that the quantity of nitrogen 
built up into higher compounds was measurably increased over 
normal. In a later paper Fred (21) corroborated his earlier 
results and concluded that while after treatment with carbon 
disulphide the soil showed a reduction in the number of micro- 
organisms, it was followed by a great increase and an increase 
also in the by-products of their action. With relatively strong 
applications of carbondisulphide to the soil, corn and oats 
seemed deleteriously affected, while mustard and buckwheat 
were benefitted, as shown by increase in dry weight. In acid 
soil, clover is also stimulated. 
e experiments described below, which further test the 
effect of carbon disulphide on plants, were performed in the 
