FORM-ALTERATIONS AND GROWTH OF CACTI. 



11 



at several places along- the same furrow. Here, if at all, uniformity might 

 have been expected; but much variation was found, as may be seen by 

 inspection of curves VI to IX, fig. 6. 



Probably these variations are the result of a combination of factors not 

 easily differentiated. The following simple experiment at least reveals a 

 mechanical condition which makes such changes possible: 



A section 35 cm. long, with a diameter of 25 cm., weighing 30 pounds 

 6 ounces, was cut from a sahuaro trunk and brought into the laboratory. 



I 1906 

 J an .24 29 



^-90- 



80 



70 



100 



Vn 90 



80 



70 



120 



vm--- 



110 



roo 



ix: 90 



80 

 70 

 60 



Feb. 

 68 n 



5 6 Ml 



.,f^\3'8 



March 



3 6 10 14 17 1 



April 



7 10 n 20 26 



May 



June 



26 



Fig. 6. — Curves from four intervals in the same furrow of sahuaro No. 12, 

 showing local variation. January 24 to June i, 1906. 



About 3 hours after cutting- it was set up on the lower cut end and a bell- 

 jar, which covered the surface to the inner edges of the furrows, was 

 placed on the upper end to prevent evaporation. A circle of spines was 

 removed and the circumference, measured by a metal tape-line, was 77.1 

 cm. On the following day the circumference had decreased 3 mm. and the 

 ends had shrunk in, forming cavities holding 400 c.c. The shrinkage 



