498 MODIFIED CIKCUMNUTATION. CHAP. X 



seen how gradually circumnutation becomes changed into apogeo- 

 tropism, under circumstances to be specified 

 in each instance. 



Rubus idceus (hybrid). A young plant, 11 

 \ inches in height, growing in a pot, was placed 



J horizontally; and the upward movement was 

 -g, traced during nearly 70 h. ; but the plant, 

 though growing vigorously, was not highly 

 *& ~j sensitive to apogeotropism, or it was not 

 ^ capable of quick movement, for during the 

 |> a . above time it rose only 67. We may see in 

 2 -|f the diagram (Fig. 184) that during the first 

 ** day of 12 h. it rose in a nearly straight line. 

 ^ When placed horizontally, it was evidently 

 "2^ circumnutating, for it rose at first a little, 

 J^Ji notwithstanding the weight of the stem, and 

 3 then sank down ; so that it did not start on 

 Jo its permanently upward course until 1 h. - 

 -a 25 m. had elapsed. On the second day, by 

 J S which time it had risen considerably, and 

 ^ 1 when apogeotropism acted on it with somewhat 

 | 2 less power-, its course during 15 3 h. was clearly 

 % .*? zigzag, and the rate of the upward movement 

 B* was not equable. During the third day, also 

 of 15 2 h., when apogeotropism acted on it 

 ] with still less power, the stem plainly circum- 

 S ^. nutated, for it moved during this day 3 times 

 oo up and 3 times down, 4 times to the left and 

 | 2 4 to the right. But the course was so complex 

 2 that it could hardly be traced on the glass. 

 2 " We can, however, see that the successively 

 8 2 formed irregular ellipses rose higher and 

 g^ higher. Apogeotropism continued to act on 

 * a the fourth morning, as the stem was still 

 ^^ rising, though it now stood only 23 from the 

 perpendicular. In this diagram the several 

 &~* stages may be followed by which an almost 



J rectilinear, upward, apogeotropic course first 

 becomes zigzag, and then changes into a 

 J circumnutating movement, with most of the 

 t successively formed, irregular ellipses directed 



upwards. 

 LUium auratum. A plant 23 inches in height was placed 



