18 



CIRCUMNUTATION OF SEEPLINGS. Chap. 1 



begun to fall, and a dot was made on a fresh glass. The move- 

 ment was traced until 5.30 p.m. as shown in (Pig. 8), which is 

 given, because the course followed was much more irregular 



than on the two previous 



Fig. 8. 



Brassica oterocea : conjoint circumnutation 



occasions. During these 

 8 hours the bead changed 

 its course greatly 10 times. 

 The upward movement of 

 the cotyledon durii^ the 

 afternoon and early part 

 of the night is here plainly 

 shown. 



As the filaments were 

 fixed in the three last 

 cases to one of the coty- 

 ledons, and as the hypo- 

 cotyl was left free, the 

 tracings show the move- 

 ment of both organs con- 



of the hypocotyl and cotyledons during joined ; and we noW 

 8 hiiurs. Figure here reduced to one- wished to ascertain whe- 

 third of the original scale, as traced on a ^j^gj. j^g^jj circumnutated. 

 vertical glass. _., , j.i i? 



Tilaments were therefore 



fixed horizontally to two hypocotyls close beneath the petioles 

 of their cotyledons. These seedlings had stood for "two days 

 in the same position before a north-east window. In the morn- 

 ing, up to about 11 A.M., they moved in zigzag lines towards 

 the light; and at night they again became almost upright 

 through apogeotropisln. After about 11 a.m. they moved a 

 little back from the light, often crossing and recrossing their 

 former path in zigzag lines. The sky on this day varied much 

 in brightness, and these observations merely proved that the 

 hypocotyls were continually moving in a manner resembling 

 circumnutation. On a previous day which was uniformly 

 cloudy, a hypocotyl was firmly secured to a Kttle stick, and 

 a filament was fixed to the larger of the two cotyledons, and its 

 movement was traced on a vertical glass. It fell greatly from 

 8.52 A.M., when the first dot was made, till 10.55 a.m. ; it then rose 

 greatly until 12.17 p.m. Afterwards it fell a little and made a 

 loop, but by 2.22 p.m. it had risen a little and continued rising 

 till 9.23 P.M., when it made another loop, and at 10.30 p.m. was 

 again rising. These observations show that the cotyledons move 



