MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 313 



an auxograph. The preparation was placed near the south end of 

 an unheated glass house with the result that the temperature of the 

 body fell as low as 4° C. at 7 A.M., and reached a point at which 

 growth ceased at about 8 P.M. The steadily decreasing temperature 

 was accompanied by a shrinkage — due in all probability to lessened 

 imbibition capacity as a result of low temperature. Resumption of 

 growth took place in the forenoon at temperatures about identical 

 with those of the previous year. The total daily growth amounted 

 to as much as 1.25 mm. to 1.5 mm. daily all of which was made 

 between 9 A.M. and 8 P.M. (Fig. 4). 



The record of growth of Carnegiea included measurements of 

 the variations in the length of the spine as well as of coincident 

 readings of the swelling of the apical region of the stem near the 

 base of the spine. 



Elongation of the spine on daily rising temperatures began at tem- 

 peratures of 24° C, 18° C, 18° C, 15° C, 13° C. and 13° C. on sepa- 



FiG. 5. Auxographic record of elongation of spine of Carnegiea April 

 3 to April 10, 1916, showing nocturnal cessation of growth. Dotted line shows 

 maxima, minima and course of air temperature (upper half of cut). Record 

 of growth of spine of Carnegiea, April 12 to April 16, 1916. Continuous 

 growth with only slight variation in rate. Dotted line shows maxima, minima 

 and course of air temperature (lower half of cut). 



