Mason — Note on Growth of Bitter Cassava. 



107 



Table 2. 



"Weight of tuberous roots and stem, and height of stem in ringed and unringed 

 plants at termination of experiment. 



The Weekly Groivth Increments. 



The weekly growth increments, which are exhibited graphically in the figure, 

 demonstrate that the velocity at which the axis elongated was in both groups 

 slow initially, became more rapid, and then declined. At the end of the eleventh 

 week the rate again increased, and then declined once more. As weekly 

 measurements were not made between the seventeenth and the twenty-seventh 

 weeks, owing to the temporary absence of the writer from the colony, information 

 is not available as to how the rate of growth varied throughout this period. The 

 total growth made by the ringed plants in this ten-week period was, however, only 

 33'6 per cent, less than in the unringed. 



In comparing the growth made by the two groups, it will be observed that 

 growth ran almost parallel up to the eleventh week, between which and the 

 twelfth week the ringing operation was performed. It would seem that any 

 divergences shown sulDsequently may confidently be referred to the removal of 

 the ring of extra-xyliary tissues. For the three following weeks, that is to say, 

 during the twelfth, thirteenth, and fourteenth, the rate of growth still continued 

 to run almost parallel. After this the ringed plants commenced to lag somewhat 

 behind the others. It would seem legitimate to refer this lag to the absence of 

 growth in the xylem, occasioned by the cessation of, or a marked retardation in, 

 the activity of the cambium below the ring. 



T 2 



