500 



MODIFIED CIECUMNUTATION. 



Chap. X 



Fig. 186. 



4°is'p.m, 



ffjn'^m. \ 



Pkalaris Canariensit : jpogeotropio move- 

 ment of cotyledon, traced on a vertical 

 and horizontal glass, from 9.10 A.M. Sept. 

 I9th to 9 A M. 20th. Figure here re- 

 duced to one-fifth of original scale. 



protrude whilst the fol- 

 lowing observations were 

 being made, was placed 

 at 10° beneath the horizon, 

 and it rose only 59° in 

 24 h. It behaved rather 

 differently from any other 

 plant, observed by ns, for 

 during the first 4i h. it 

 rose in a line not far from 

 straight; during the next 

 64 h. it circumnutated, 

 that is, it descended and 

 again ascended in a 

 strongly marked zigzag 

 course; it then resumed 

 its upward movement in 

 a moderately straight line, 

 and, with time allowed, 

 no doubt would have be- 

 come upright. In this 

 case, after the first 4J h., 

 ordinary circumnutation 

 almost completely con- 

 quered for a time apogeo- 

 tropism. 



Brassica oleracea. — The 

 hypocotyls of several 

 young seedlings placed 

 horizontally, rose up ver- 

 tically in the course of 6 

 or 7 h. in nearly straight 

 lines. A seedling which 

 had grown in darkness to 

 a height of 2i inches, and 

 was therefore rather old 

 and not highly sensitive, 

 was placed so that the 

 hypocotyl projected at be- 

 tween 30° and 40° beneath 

 the horizon. The upper 

 part alone became curved 



