Cahi'. I. 



PKIMULA. 



45 



filament was, as far as could be ascertained, about 'U of an 

 inch. 



Helirtnthus annuus (Compositai). — The upper part of the 

 hypocotyl moved during the 

 day-time in the course 

 shown in the annexed figure 

 (Fig. 32). As the hne runs 

 in various directions, cross- 

 ing itself several times, 

 the movement may be con- 

 sidered as one of circumnti- 

 tation. The extreme actual 

 distance travelled was at 

 least •! ojf 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 mndow 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 slaking without 

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

 due to the absence of light. 



Frimuld Sinensis (Primulacete). — 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 tha 

 day and night. The movements of the same seedling were traced 



Hdianthus annuus : circumautation of 

 hypocotyl, with filament fi.\-ed 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 

 magniHed 21 times, here reduced to 

 one-half of original scale. 



