516 



MODIFIED CIRCUMNUTATION. 



Chap. X. 



which was already curved 36° beneath the horizon, was observed 

 from 11 A.M. July 22nd to the 27th, by which latter date it 

 had become vertically dependent. Its course during the first 

 12 h. is shown in Fig. 190, and its position on the three 

 succeeding mornings until the 25th, 

 when it was nearly vertical. 'During 

 the first day the peduncle clearly 

 circumnutated, for it moved"^ times 

 down and 3 times up; and on each 

 succeeding day, as it sank downwards, 

 the same movement continued, but 

 was only occasionally observed and 

 was less strongly marked. It should 

 be stated that these peduncles were 

 observed under a double skylight in 

 the house,' and that they generally 

 moved downwards very much more 

 slowly than those on plants growing 

 out of doors or in the greenhouse. 



The movement of another vertically 

 dependent peduncle with the flower- 

 head standing half an inch above the 

 ground, was traced, and again when 

 it first touched the ground; in both cases irregular ellipses 

 were described every 4 or 5 h. A peduncle on a plant which 

 had been brought into the house, 

 moved from an upright into a ver- 

 tically dependent position in a 

 single day; and here the course 

 during the first 12 h. was nearly 

 straight, but with a few weU-marktd 

 zigzags which betrayed the essential 

 nature of the movement. Lastly., 

 the circumnutation of a peduncle 

 was traced during 51 h. whilst in 

 the act of burying itself obliquely 

 - in a little heap of sand. After it had buried itself to such a 

 depth that the tips of the sepals were alone visible, the above 

 figure (Fig. 191) was traced during 25 h. When the flower- 

 head had completely disappeared beneath the sand, another 

 tracing was made during 11 h. 45 m. (Fig. 192) ; and here again 

 we see that the peduncle was circumnutating. 



Tr^fiiUum su'derraneum ; cir- 

 cumnutating movement of 

 peduncle, whilst the flower- 

 head was burying Itself in 

 sand, with the reflexed tips 

 of the calyx still visible ; 

 traced h-om 8 A.M. July 

 26th to 9 A.M. on 27th. 

 Glass filament fixed trans- 

 versely across peduncle, 

 ■near flower- head. 



Tig-. 192. 



Trifo'iuin suhterraneum ; move- 

 ment of Siime peduncle, with 

 flower-head completely buried 

 beneath the sand ; traced from 

 8 A.M. to 7. 1 5 P.M. on July 29th. 



