CHAPTER VII. 



CURVATUEES. 



SECTION A. Geotropism. 



SECTION B. Decapitation experiments, curvatures due to in- 

 jury, to contact, to unequal turgidlty, to 

 jiaccidity. 



SECTION C. Heliotropism. 



SECTION D. Diaheliotropism, Diageotropism, epinasty, nuta- 

 tion of epicotyls. 



SECTION A. Geotropism. 

 (191) Region of curvature coincident with region of growth. 



If the curvature is to be observed in damp air a bean- 

 root of not more than 15 mm. in length answers best. 

 It should be marked at intervals of 2 mm. and pinned 

 to the lid of a stoppered jar half full of water; the jar 

 should be occasionally inverted for a moment or two so 

 as to thoroughly wet the seedling and the cork. After 

 12 hours measure the distance between the marks, 

 which gives the region of greatest growth, and note the 



112 



