50 Lewis Knudson 



not only to an increased rate of respiration, but also to the fact that the 

 root systems of the sugar-fed plants are greater than those of the check 

 plants. This fact is brought out in table 19, and, in the case of the glucose 

 and the check cultures, in figure 9. 



All the data for this experiment are summarized in table 19. Since 

 the respiration figures for the first three days were not obtained for all 

 the cultures, it was necessary to make an estimate for these days in order 

 to get an idea of the total carbon dioxide evolution. The estimated 

 figure, given in the ninth column of the table, is 85 milligrams. This 

 figure is based on the results obtained as given in table 18, and also on 

 the results of a similar experiment in which the entire carbon dioxide 

 evolution was determined. The figure is perhaps a little low, rather 

 than high, and furthermore no distinction is made between the carbon 

 dioxide evolved by the checks and that evolved by the sugar-containing 

 cultures. The difference for this period, however, would be slight and 

 would not at all affect the general conclusions. 



An examination of table 19 reveals data of considerable interest. In 

 general the dry weights of the roots of the sugar-fed plants are approxi- 

 mately double those of the check cultures. This is shown in figure 9 

 in the case of one of the glucose cultures. The weights of the tops in 

 the various cultures show considerable similarity, although the sugar 

 cultures average higher than the check cultures. It would appear that the 

 behavior of the roots is very similar to that of a purely saprophytic 

 organism. 



It is of interest to note that the saccharose cultures and one of the 

 glucose cultures showed a gain in weight over the original dry weight of 

 the seed. The maltose and the glucose are not so beneficial as the saccha- 

 rose. The sugar-fed cultures, as was to be expected, showed a greater 

 growth than the checks, -and a greater carbon dioxide evolution. The 

 failure to lose in dry weight is not due to a conservation of the reserve 

 food of the seed, but to the absorption of sugars, this absorbed food 

 permitting greater growth, resulting in an increase in dry weight. 



The glucose and starch equivalents of the carbon dioxide evolved are 

 given in the last two columns. In the case of those cultures that showed 

 a gain in weight, it would be logical to assume that the sugar absorbed 

 equaled approximately the glucose equivalents. Unfortunately the sugar 



