FORM-ALTERATIONS AND GROWTH OF CACTI. 



21 



Table 4. — Difference of internal temperature on the southeast and northwest sides of same 

 plant for 24- hours in June and November. 



ID 40° 



I S.E. 



<u 30° 



<= N.W. 



Fig. 11. — ^Curves showing differences of internal temperature on opposite sides of 

 sahuaro trunk, constructed from data in table 4. Each vertical space rep- 

 resents 10° F. and each horizontal space i hour. The two upper curves 

 should be crossed somewhere between 8''3o"' p.m. and 4''4o'" a. m. 



