w 



CIRUUMNUTATION OF SEEDLINGS. 



Chap. I 



Fig. 37. 



Nolana prostrata (Nolanea). — The movements were not 

 traced, but a pot with seedlings, which had been kept in the 

 dark for an hour, was placed under the microscope, with the 

 micrometer eye-piece so adjusted that each division equalled 

 ^th of an inch. The apex of one of the cotyledons crossed 

 rather obliquely four divisions in 13 minutes ; it was also sink- 

 ing, as shown by getting out of focus. The seedlings were 

 again placed in darkness for another hour, and the apex now 

 crossed two divisions in 6 m. 18 s. ; that is, at very nearly the 

 same rate as before. After another interval of an hour in dark- 

 ness, it crossed two divisions in 4 m. 15 s., there- 

 fore at a quicker rale. In the afternoon, after a 

 longer interval in the dark, the apex was motion- 

 less, but after a time it recommenced moving, 

 though slowly ; perhaps the room was too cold. 

 Judging from previous cases, there can hardly 

 be a doubt that this seedling was circumnuta- 

 ting. 



Solanum lycopersicum (Solanefe) ^The move- 

 ments of the hypocotyls of two seedling to- 

 matoes were observed during seven hours, and 

 there could be no doubt that both circumnu- 

 tated. They were illuminated from above, but 

 by an accident a little light entered on one side, 

 and in the accompanying figure (Fig. 37) it 

 may be seen that the hypocotyl moved to this 

 side (the upper one in the figure), making small 

 loops and zigzagging in its course. The move- 



SoJanum lycoper- 

 sicum : circunj- 

 nutation of hy- 

 pocotyl, with 

 filament fixed 

 across its sum- 

 mit, traced on 

 horizontal glass, 

 from 10 A.M. to 

 5i'.M.0ct.24th 



Ilhnninated ob- ments of the cotyledons were also traced both 

 on vertical and horizontal glasses ; their angles 

 with the horizon were likewise -measured at 

 various hours. They fell from 8.30 a.m. (October 

 17th) to about noon ; then moved laterally in a 

 zigzag line, and at about 4 p.m. began to rise; 

 they continued to do so until 10.30 p.m., by 

 which hour they stood vertically and were asleep. 

 At what hour of the night or early morning they began to fall 

 was not ascertained. Owing to the lateral movement shortly 

 after mid-day, the descending and ascending lines did not 

 coincide, and irregular ellipses were described during each 24 h. 

 The regular periodicity of these movements is destroyed, as W8 

 shall hereafter see, if the seedlings are kept in the dark. 



liquely from 

 above. llove- 

 ment of bead 

 magnified about 

 35 times, here 

 reduced to one- 

 third of original 

 scale. 



