50 CIECUMNUTATION OF SEEDLINGS. CHAP. L 



Nolana prostrata (Nolaneae). The movements were not 

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

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

 micrometer eye-piece so adjusted that each division equalled 

 g^o-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- 

 Fig. 37. f ore at a quicker rate. 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. 



Solatium ly coper sicum (Solanese). The move- 

 ments of the hypocotyls of two seedling to- 

 Solanum ly coper- matoes were observed during seven hours, and 

 sicum: circum- there could be no doubt that both circumnu- 

 n *tion ofjiy- tated< They were illuminated from above, but 

 filament fixed ^ v an accident a little light entered on one side, 

 across its sum- and in the accompanying figure (Fig. 37) it 

 mit, traced on may be seen that the hypocotyl moved to this 



fromTo A.M* to side ( the ^PP 6 * one in the fi S ure )> making small 

 5 P.M. Oct. 24th. loops and zigzagging in its course. The move- 

 Illuminated ob- ments of the cotyledons were also traced both 

 liquely from on ver ti ca i an d horizontal glasses ; their angles 

 men t e ' O f ^ead wittl the h rizon were likewise measured at 



magnified about various hours. They fell from 8.30 A.M. (October 

 35 times, here 17th) to about noon ; then moved laterally in a 



So? original zi S za g line > and at ab ut 4P ' M - be S ant ris6 ' 

 sca l e< 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 wo 

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



