OHM-. L 



PRIMULA. 



46 



filament was, as far as could be ascertained, about "14 of an 

 inch. 



Udianthus annuus (Composite). The upper part of the 

 hypocotyl moved during the 



day-time in the course Fig- 32. 



shown in the annexed figure 

 (Fig. 32). As the line runs 

 in various directions, cross- 

 ing itself several times, 

 the movement may be con- 

 sidered as one of circumnu- 

 tation. The extreme actual 

 distance travelled was at 

 least '1 of an inch. The 

 movements of the cotyle- 

 dons of two seedlings were 

 observed; one facing a north- 

 east window, and the other 

 so feebly illuminated from 

 above as to be almost in 

 darkness. They continued 

 to sink till about noon, 



when they began to rise ; but between 5 and 7 or 8 P.M. 

 they either sank a little, or moved laterally, and then again 

 began to rise. At 7 A.M. on the following morning those on 

 the plant before the north-east window had opened so little 

 that they stood at an angle of 73 above the horizon, and were 

 not observed any longer. Those on the seedling which had 

 been kept in almost complete darkness, sank during the whole 

 day, without rising about mid-day, but rose during the night. 

 On the third and fourth days they continued sinking without 

 any alternate ascending movement; and this, no doubt, was 

 due to the absence of light. 



Primula sinmsis (Prinmlacere). A seedling was placed with 

 the two cotyledons parallel to a north-east window on a day 

 when the light was nearly uniform, and a filament was affixed 

 to one of them. From observations subsequently made on 

 another seedling with the stem secured to a stick, the greater 

 part of the movement shown in the annexed figure (Fig. 33), 

 must have been that of the hypocotyl, though the cotyledons 

 certainly move up and down to a certain extent both during the 

 day and night. The movements of the sa.i.c secdli ng were traced 



Ifelianfhus annuus : circumnutation of 

 hypocotyl, with filament fixed across 

 its summit, traced on a horizontal 

 glass in darkness, from 8.45 A.M. to 

 10.45 P.M., and for an hour on follow- 

 ing morning. Movement of bead 

 magnified 21 times, here reduced to 

 one-half of original scale. 



