Growth in Eriogonum nudum 215 



received on a smoked drum, was perfectly clear cut and smooth, except 

 when certain movements^ caused sudden very slight deflections. 



The character of the material and the effectiveness of the instru- 

 mentation were such as to achieve an interpretable record of growth 

 rates of less than o.i mm. per hour, while the changes of rate following 

 the imposition of experimental conditions were readily observable 

 within a few minutes. Thus, on July 9, after cutting through the basal 

 long intemode, the shrinkage thereby induced began in five minutes. 

 Earlierinthecourseof events, when normal shrinkage was being recorded, 

 this was observed to cease at once on the removal of the basal leaves 

 and positive growth in measurable values was recorded in 18 minutes. 



July 9th. Beginning with 10.42 hour reading^ (fig. 7), 

 Minutes: 60 15 45 60 60 Leaves cut i8 20 Basal internode 5 5 5 5 5 5 5 

 Growth: 20 5 -5-15-25 off at 13.42 5 10 entirely ampu- o -20-25-13 -7-6 o 



hr. tated. 



Data obtained. — Complete growth records for fifty-five days giving 

 the partial or for the greater part nearly entire growth history of six 

 different intemodes. It was of course not possible with the method 

 used to begin a record before the internode had attained sufficient 

 stature to permit the necessary instrumental adjustments to be made. 

 The youngest one was 15 mm. in length at the beginning of the record. 

 For the sake of economy the basic data are not given in their entirety. 

 The accompanying graphs, however, summarize the whole array of 

 data sufficiently for the purpose (figs. 3, 4) . The records of growth on 

 days of alternating sunshine and fog, and on which no experimental con- 

 ditions were imposed have been omitted, except that their effect on 

 the numbers expressing the average growth for the whole period of 

 53 days is included in the graphs of figs. 3 and 4. The complete records 

 for the day period for days of continuous sunshine and of continuous 

 fog, and for those on which responses to special experimental conditions 

 occurred are given. 



The numbers given in the tables which follow express in millimeters 

 the movement of the writing arm of the recording lever, which amplified 

 the growth movement sevenfold. These numbers are always used 

 except when otherwise stated. 



^ These movements were recorded as sharp serrations above the general course of the 

 growth curve, the steep side of the tooth indicating a sudden shortening of the growing 

 part, and the less steep side a slower recovery. They occurred with a periodicity of 

 20 to 30 per hour. An investigation of nutational movements showed that these also 

 occurred, but with quite a different periodicity. It is purposed to give a fuller account 

 of the movements in question at a later date. 



^ In the protocols which follow, the rates of growth are given as recorded instru- 

 mentally, and to obtain absolute values in mm. must be subjected to the correction xi/7. 



