208 



COLLINS AND KEMPTONI A FIELD AUXANOMETER 



for use in the open, has seriously retarded the accumulation of infor- 

 mation regarding individual and varietal diversity in the reaction of crop 

 plants to changes in environment. In designing the present instru- 

 ment, therefore, an effort was made to use only the cheapest material 

 and the simplest form of construction, so that the cost might be kept 

 down to a point that would permit the use of the instrument in sufficient 

 numbers to acquire extensive data for statistical treatment . 



ID U 12 12 34-S6 7S9 10 111E.1E3AS67 3 9 lO 11 12 



NOON P.M. MIDNIGHT A.M. NOON 



Fig. 3. Graph of hourly elongation, taken from record shown in figure 2. 



Our observations on the rate of elongation in maize plants 

 have led to the belief that in many of the investigations of peri- 

 odicity in growth individual variation in the plants has not been 

 adequately considered. For example, it was found that some 

 plants showed a definite reduction in the rate of elongatidh be- 

 tween the hours of 8 and 10 a.m., while other plants of the same 

 variety showed no such reduction. To detect differences of this 

 kind it is necessary to secure records from a number of plants 

 simultaneously, for if the records were taken on different days 

 it would be difficult to exclude the possibility that differences in 

 behavior were due to differences in the climatic conditions. 



In many investigations it is equally important that measure- 

 ments should be made on plants growing naturally in the field. 

 With maize, at least, results obtained under greenhouse or lab- 

 oratory conditions are quite at variance with results obtained 

 in the open. In our experiments the only maize plants to ex- 

 hibit a greater rate of elongation at night than in the day have 



