THE SECRETION OF INVERTASE BY PLANT ROOTS 
373 
with cotton. The two flasks are then sterihzed in an autoclave for 30 
minutes at a pressure of 15 pounds. When the solutions are cool, solution B 
is poured into the culture flask containing solution A. This transference of 
solution B to A takes place under conditions to minimize as much as possible 
the possibility of contamination. The funnel is then replaced by a cotton 
stopper and the cotton stopper and neck of the flask are covered again with 
cotton to prevent organisms and spores from lodging in the cotton stopper^ 
circumstances which might cause contamination when the seedling is 
transferred to the culture flask. The flasks are permitted to stand several 
days before the seedlings are transferred, and at the time of transplanting 
any that show contamination are rejected. 
Hydrogen-ion determinations were made by the indicator method, using 
mixtures of monobasic potassium phosphate and dibasic sodium phosphate- 
prepared according to the methods of Soerensen (Prideaux, 7). These 
determinations were made at the outset of the experiment and also at its- 
conclusion, and in some experiments mentioned subsequently the reaction 
of the culture solution was followed by adding to the culture solution the 
indicator, neutral red. The hydrogen-ion concentration is expressed as 
the logarithm (the base being 10) of the normality with respect to the 
hydrogen ions. The minus sign is understood; for example, P[H]7 refers 
to a hydrogen-ion concentration of io~'^ normal. 
Sugar determinations in experiment i were made by Kendall's method 
(2), and the reducing sugar is expressed as invert sugar. In all the other 
experiments the volumetric method of Cole (i) was used. This method 
proved to be a rapid and accurate method for the purpose. The reducing 
sugars are expressed as glucose. In the use of both methods the solutions 
were standardized against prepared sugar solutions, the sugars used being 
of a very high degree of purity. 
Experiments 
Experiment i. In this experiment Canada field pea {Pisum arvense L.) 
was used. The culture vessels were pyrex flasks of one-liter capacity and the 
quantity of the nutrient solution was 1050 cc. Sterilization of the solutions 
was effected by autoclaving at 15 pounds pressure for 30 minutes. Seeds 
were sterilized by the use of calcium hypochlorite for one hour. The 
plants were grown in a greenhouse at an average temperature of 70° C. 
At the conclusion of the experiment the culture solutions were tested for 
sterility by plating i cc. of each solution on an agar medium of Pfeffer's 
solution plus I percent sucrose. Only those cultures that proved to be 
sterile were analyzed. The results follow in table i and a typical culture is 
shown in figure i. 
There is in each of the culture solutions containing sucrose an appreciable 
gain in reducing sugars, but the gain is relatively slight as compared to the 
total amount of sucrose present. If the enzyme invertase is secreted, why 
