52 Lewis Knudson 



determinations were not made. Qualitative tests showed the presence 

 of reducing sugars in the media containing saccharose. 



The results of the experiment are in agreement ^\^th the results obtained 

 by Maige and Nicolas (1910) and contrary to the conclusion of Palladine 

 (1901) — though it is hardly to be expected that the data from long- 

 continued respiratory rates should agree with that for a short-period 

 rate. Saccharose and glucose are somewhat similar in their beneficial 

 effects, the former being slightly better than glucose, and glucose better 

 than maltose. 



Four attempts were made to repeat this experiment, but in every 

 case the results had to be discarded owing to the occurrence of con- 

 taminations in nearly all the culture vessels. In every case the 

 contamination was due to the introduction of one or two dead seeds 

 into -the growth chamber. It appeared to be almost impossible to sterilize 

 the dead seeds, and no means was available for their detection; although 

 it was noted in general that the failure of vetch seeds to bleach in the 

 hypochlorite solution was indicative of failure to germinate. One pre- 

 liminary experiment, in which glucose alone was tested in its effect on 

 growth and respiration, yielded results similar to those obtained with 

 that sugar in the experiment already described. 



INFLUENCE OF VARIOUS CONCENTRATIONS OF SUGARS ON PLANT GROWTH 

 MoUiard (1907) has shown that increasing the concentration of sugar 

 beyond 2 per cent effects a corresponding increase in the dry weight 

 of plants, although the higher concentrations do not permit of normal 

 plant development. No investigations have been made on the influence 

 of a series of lower concentrations of sugars on plant growth, and from 

 the practical standpoint this is of greater importance; for it is evident 

 that if organic matter is directly absorbed by a plant growing under 

 normal conditions, then the plant must have the ability to take from 

 the soil solution organic substances present in extremely weak concen- 

 trations. Aside from the practical aspect of the question, information on 

 the subject is desirable for purely physiological reasons. Investigations were 

 accordingly made with cabbage, sweet clover, crimson clover, and vetch. 



EXPERIMENTS WITH CABBAGE (BRASSICA OLERACEA L.) 



In the experiments with cabbage large test tubes were employed as 

 culture vessels, each containing 50 cubic centimeters of the nutrient 



