Growth in Eriogonum nudum 221 



growth of this day was quite exceptional. The part was quite thick and 

 young, 31 mm. long, and was subjected to high temperatures. Instead 

 of the usual morning period of shrinkage there were three periods of 

 reduced growth rates, while the period of major growth was postponed 

 till late in the afternoon (table 3). 



The period following the critical hour of maximum early morning 

 growth, which falls, as above said, on any hour from 6 to 9, but which 

 usually occurs at 7 to 8, is one of either much reduced growth rate, or 

 net shrinkage. The latter condition occurred on 31 of 53 days. 



The maximum value for this shrinkage (measured 8-10 hours on 

 August 30th) during the period was 0.9 mm. the internode having been 

 88 mm. long at the beginning of the day's growth. It was the observa- 

 tion of this behaviour in 19 12 that furnished the impetus to the work, 

 at which time it was noted that the terminal internodes frequently 

 wilted sufficiently to become pendulous (Lloyd, '12). The direct measure- 

 ment of several long internodes discovered either cessation of growth, 

 or, when wilting was evident, maximum shrinkages of 1-1.5 mm. being 

 about 2 to 3 per cent, on the length of the growing portion. It was 

 noted that at the time the auxanometer was registering shrinkage, the 

 growing internodes of nearby plants showed wilting, though of course 

 the part serving for measurement did not alter its form except longi- 

 tudinally because of the pull — of about 3 grams — of the lever. Although 

 the plants studied in 19 16 showed this behaviour usually between 8 and 

 10 hour, the measurements of 191 2 indicate that this is not always the 

 case but is modified by various surrounding conditions. The plants 

 studied in 19 12 were growing in another place and were shaded by trees 

 during the first half of the morning. Recurring to the conditions of 191 6 

 on days of continuous sunshine (table 3 ; fig. 6) the shrinkage commenced 

 at about the same time as on foggy days but advanced to absolute values 

 of about twice those of foggy days. The period of slackened growth was, 

 however, generally more prolonged on foggy days, on which also there 

 were lower recovery rates between 10 and 14 hours (graph 3, fig. 6). 

 When the temperatures were abnormally high, as when the part was 

 enchambered behind uviol glass, the shrinkage was induced about an 

 hour earlier (at 9 hour) and proceeded to absolute values slightly greater 

 than those for sunny days with normal temperatures. With higher 

 temperatures and sunlight the greater part of the shrinkage was more 

 usually accomplished during the earlier phase of the process, while 

 under normal temperatures the shrinkage became accelerated during 

 the later phase as frequently as not. 



The rise in growth rates at the conplusion of the period of slackening 

 or shrinkage was invariably shown. On days of continuous sunshine 



