498 MODIFIED CIRCUMNUTATION. CHAP. X 



seen how graduaJly circumnutation becomes changed into apogeo- 

 tropism, under circumstances to be specified 

 in each instance. 



Rubus idceus (hybrid). A young plant, 11 

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

 ,- _ horizontally; and the upward movement was 



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

 though growing vigorously, was not highly 

 -2 sensitive to apogeotropisin, or it was not 

 jj capable of quick movement, for during the 



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

 |? the diagram (Fig. 184) that during the first 



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

 *j When placed horizontally, it was evidently 

 ^ circumnutating, for it rose at first a little, 

 ^ notwithstanding the weight of the stem, and 

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

 % its permanently upward course until 1 h. 

 ^g 25 m. had elapsed. On the second day, by 

 g which time it had risen considerably, and 



1 when apogeotropism acted on it with somewhat 



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

 .SP zigzag, and the rate of the upward movement 



was not equable. During the third day, also 



% of 15| h., when apogeotropism acted on it 



^ with still less power, the stem plainly circum- 



*. nutated, for it moved during this day 3 times 



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



3 4 to the right. But the course was so complex 

 that it could hardly be traced on the glass. 

 ^ We can, however, see that the successively 

 "! formed irregular ellipses rose higher and 

 .S higher. Apogeotropism continued to act on 



* the fourth morning, as the stem was still 

 o rising, though it now stood only 23 from the 

 ,d perpopdicular. In this diagram the several 

 >"~ l stages may be followed by which an almost 

 i | rectilinear, upward, apogeotropic course first 



f becomes zigzag, and then changes into a 



f J circumnutating movement, with most of the 



y fc$ successively formed, irregular ellipses directed 



upwards. 

 Ltlium anratum. A plant 23 inches in height was placed 



