73 BOTANICAL GAZETTE [SEPTEMBER 
grew in the sixth period. All the roots still growing were acciden- 
tally lost in the sixth period. 
An examination of the data in table V and the curves in fig. 7 
shows that none of the yeast concentrations prevented the gradual 
decrease in length gain, secondary root production, and dry matter 
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1G. 7.—Growth in length of excised corn root tips in dark for five periods of 
transfers; solutions used were Pfeffer’s solution plus 2 per cent glucose (check), and 
same solution plus 80, 200, 400, or 800 ppm autolized yeast. 
elaboration. The rate of decrease was very rapid at first, but 
became less so as the periods passed. The increase in the rate of 
growth in 400 ppm of autolized yeast in the fifth period is apparent 
only. It is due to the fact that two roots only out of the eight of the 
fourth period grew in the fifth period. Their growth was excellent 
throughout the experiment, but decreased continuously. The 
