MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



67 



Comment on Figs. 19 and 20. The rate of growth of the scape 

 is represented by the continuous line and the actual elongation 

 during every period of two hours is denoted by half the distance of 

 this line from the base line measured from the point over the numer- 

 als denoting the hours. 5, 10 and 20 millimeter intervals are 

 marked on the left hand margin for convenience. The course of 

 temperature is designated by the dotted line, and the single reference 

 point of 20P C. is marked on the right hand margin of the plans. 

 The temperature is seen to range from 15° to 25° C, and the maxi- 

 mum rate of growth of about 11 mm. for the two-hour period ending 

 at 6 p. m. on March 30. During the last 12 hours of the observa- 

 tions the total amount of growth did not exceed 3 mm. and the 

 preparation was removed to the dark room with the result that an 

 immediate acceleration of growth was shown as illustrated in Fig. 21. 



5min 



A 



5 6 7 8 9 10 11 12 



5inm 



B 



13 14 15 16 17 18 19 20 



Fig. 21. A, curve of growth of normal peduncle placed in dark chamber at con- 

 stant temperature of 19 to 21° C Maximum rate of elongation of 3 mm. in a 2-hour 

 period was shown. B, curve of growth of a normal petiole, fully grown, then placed 

 in dark room as in A. 



Comment on Figs. 22 and 23. The curve of growth is repre- 

 sented by the irregular continuous line and was plotted from auxano- 

 metric measurements beginning when the sheathing prophyll had 

 attained a length of 10 cm. and could be opened to allow the attachment 

 of clamp of a Corbett auxanometer (see MacDougal's Practical Text- 

 Book of Plant Physiology, p. 287. 1901). The actual amount of 



