FORM-ALTERATIONS AND GROWTH OF CACTI. 



19 



ble, the process begfinning- on the southeast and advancing- on either side 

 to the northwest, so that finally the apex of the stem is encircled, wholly 

 or in part, by a crown of flowers. 

 Tablk 3. — Diference of internal temperature on north and south sides of the same plant. 



Date and time. 



Apr. 12 — 12''45'' 



I 3S 



3 oo 



6 so 



Apr. 13 — 6 40 



I 40 



S S5 

 Apr. 14— 7 35 



5SS 



Apr. IS— 7 40 



10 40 



p. m. 

 p. m. 

 p. m. 

 p. m. 

 a. m. 

 p. m. 

 p. m. 

 a. m. 

 p. m. 

 a. m. 

 a. m. 



Date and time. 



Apr. 15— I2''IS° 



2 25 



Apr. 19 — ■ I 00 



p. m. 

 p. m. 

 p. m. 



3 10 p. m. 



Apr. 20— 2 SO p. m. 



Apr. 22 — -10 00 a. m. 



11 00 a. m. 



12 00 noon 

 I 00 p. m. 



May 6- 



3 °o 



I 00 



p. m. 

 p. m. 



23 



23 



Fig. 10. — Two curves representing the sums of variations of eight intervals on 

 sahuaro No. 10 (shaded) and No. 21 (unshaded). Jan. 22 to May 21, 1909. 



