i98 MODIFIED CIRCUMNUTATION. Chap. X 



seen how gradually circumnutation becomes changed into apogeo- 

 tropism, under circumstances to be speciiied 



'^' ' in each instance. 



Ruhus idceus (hybrid). — A young plant, 11 



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



„- horizontally; and the upward moTement was 



•Si traced during nearly 70 h. ; but the plant, 



" _ though growing vigorously, was not highly 



.a -2 sensitive to apogeotropism, or it was not 



«_^ capable of quick movement, for during the 



^ fl above time it rose only 67°. We may see in 



"^ ■- the diagram (Fig. 184) that during the first 



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



'S « When placed horizontally, it was evidently 



"^ ° ciroumnutating, for it rose at first a little, 



S 3 notwithstanding the weight of the stem, and 



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



•J o its permanently upward course until 1 h. 



> T3 25 m. had elapsed. On the second day, by 



" D which time it had risen considerably, and 



° t when apogeotropism acted on it with somewhat 



S £ less power, its course during ISi h. was clearly 



i .5? zigzag, and the rate of the upward movement 



9 was not equable. During the third day, also 



; " -S of 15i h., when apogeotropism acted on it 



/ ° "^ with still less power, the stem plainly circum- 



; S 3 nutated, for it moved during this day 8 times 



/ I CO up and 3 times down, 4 times to the left and 



; g ° 4 to the right. But the course was so complex 



( H 5 that it could hardly be traced on the glass. 



£ '-' We can, however, see that the successively 



§ g formed irregular ellipses rose higher and 



g.S higher. Apogeotropism continued to act on 



.. a the fourth morning, as the stem was still 



SZ rising, though it now stood only 23° from the 



-=^3 perpendicular. In this diagram the several 



'£'"' stages may be followed by which an almost 



I rectilinear, upward, apogeotropic course first 



^ becomes zigzag, and then changes into a 



J ciroumnutating movement, with most of the 



a; successively formed, irregular ellipses directed 



upwards. 



Ldium aiirafum. — A plant 23 inches in height was placi'd 



