Spalding : Mechanical adjustment of suaharo 



65 



and light in the production 

 of the form in question. To 

 ascertain this and to find to 

 what extent temperature as 

 a secondary factor is active 

 in the expansion and contrac- 

 tion of the stem would re- 

 quire observations extending 

 over several seasons. 



It will be instructive, how- 

 ever, to compare the curves 

 already discussed with the 

 temperature record for a cor- 

 responding period. ■ From 

 January 8 to 14 the mean 

 temperature ranged from 42° 

 to 56° F., and the effect of 

 a rain of 0.2 of an inch was 

 scarcely perceptible. From 

 February 6 to 24 the mean 

 temperature ranged from 47 

 to 68^ F. and after a rain 

 of half an inch the stems 

 expanded steadily for three 

 weeks. Later than this the 

 mean temperature continued 

 to increase during the period 

 of observation, but, as al- 



w 



ready seen, the stems stead- 

 ily contracted. It is notice- 

 able, however, in comparing 



figures 8 and g, that the fur- 

 rows on the south side re- 

 sponded to the rain earlier 

 than those on the north. 



the stem. 



Figure 5. Section about 8 feet from the base, through the greatest diameter of 



Figure 6. Section five feet from the base. 



Figure 7. Section 15 inches from the base. The thin-walled, water-holding 

 tissue becomes discolored almost immediately on contact with the air. 



