1 8 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



between the two figures until 6 P.M., the rate of growth being a 

 straight Hne record. 



The major part of the growth enlargement being accomplished, 

 the newly matured joint began to exhibit the daily variations 

 hitherto displayed by the mature joint. Increase in length in 

 progress at daylight was slightly accelerated at about 8 A.M. and 

 continued with the rising temperature (May ii — 68° F.-76° F. 

 until 2:30 P.M.) then slackened, although the temperature kept 

 up to 78° F. at 8 P.M. By 4 P.M. a shrinkage began which 



Fig. 3. Auxographic tracings of growth of joint No. 5, of O/Jtni/i'a i^/a^fawa, X ifr- 

 Downward movement denotes elongation. The date of beginning of each partial record 

 is given. Thus the record of beginning April 2 extends to the evening of April 4. The 

 record for the entire week beginning April 19 is given. 



continued until about midnight, when with a temperature now 

 falling to 70° F. at 7 A.M., elongation began, and continued as 

 on the previous day, until mid-afternoon. A behavior of a modi- 

 fied type was presented by the growth of the young bud of Opiuitia 

 Blakeana No. 13, a joint which had been rooted in sand and 

 covered with a screen of glass (G55A62), which transmits only 

 the violet rays and the longer red waves, from No\-eml)er until 

 it began to develop a bud late in March, 191 5. 



April 9, 19 1 5, it was removed to the greenhouse and put in 

 contact with an auxanometer in which the compound lever mag- 

 nified the motion by 23. From the first the rate of growth was 

 accelerated, beginning at about 9 A.M. and continued at a high 

 rate until about 4 P.M. or later. Slackening then occurred and 

 the actual rate decreased until about 8 A.M. This last-named 



