496 



MODIFIED CIRCUMNUTATION. 



CHAP. X 



then suddenly began to circumnutate. A partially etiolated 



Fig. 183. 



\ 



rgffcmjs? i 



Beta 



and somewhat old hypocotyl 

 of a seedling cabbage (21 

 inches in height) was so 

 sensitive that when placed 

 at an angle of only 23 from 

 the perpendicular, it became 

 vertical in 33 minutes. As 

 it could not have been 

 strongly acted upon by 

 apogeotropism in the abovo 

 slightly inclined position, 

 we expected that it would 

 have circumnutated, or at 

 least have moved in a zig- 

 zag course. Accordingly, 

 dots were made every 3 

 minutes; but, when these 

 were joined, the line was 

 nearly straight. After this 

 hypocotyl had become up- 

 right it still moved onwards 

 for half an hour in the same 

 general direction, but in a 

 zigzag manner. During the 

 succeeding 9 h. it circum- 

 nutated regularly, and de- 

 scribed 3 large ellipses. In 

 this case apogeotropism, 

 although acting at a very 

 unfavourable angle, quite 

 overcame the ordinary cir- 

 cumnutating movement. 



The hypocotyls of Beta 

 vulgaris are highly sensitive- 

 to apogeotropism. One was 



>ta t/r;am: apogeotropic movement j d f project 19 



of hypocotyl from 19 beneath horizon 



to a vertical position, with subsequent beneath the horizon ; it fell 



circumuutation, traced on a vertical at first a very little (see 



ttitiSttSttls. *Vfj' h n t f i ; bt f n? 



Figure reduced to one-third of original to lts we] 8 ht ? bnt as lfc was 



,cal . circumnutating the line was 



