350 MODIFIED CIECUMNUTATION. Chap. VU 



With T. Pannonicum the first true leaf was generally unifoliate, 

 but sometimes trifoliate, or again partially lobed and in an 

 intermediate condition. 



Oircumnutation. — Sachs described in 1863* the spontaneous 

 up and down movements of the leaflets of T. incarnatum, when 

 kept in darkness. Pfeffer made many observations on the 

 similar movements in T. pratense.^ He states that the teraoinal 

 leaflet of this species, observed at different times, passed through 

 angles of from 30° to 120° in the course of from li to 4h. We 

 observed the movements of T. suhterraneum, resvpinatum, and 



Trifiiliiim subterranetim. — A petiole was secured close to the 

 base of the three leaflets, and the movement of the terminal 

 leaflet was traced during 26i h., as shown in the figure on the 

 next page 



Between 6.45 a.m. and 6 p.m. the apex moved 3 times up 

 and 3 times down, completing 3 ellipses in 11 h. 15 m. The 

 ascending and descending lines stand nearer to one another 

 than is usual with most plants, yet there was some lateral 

 motion. At 6 p.m. the great nocturnal rise commenced, and 

 on the next morning the sinking of the leaflet was continued 

 until 8.30 A.M., after which hour it circumnutated in the manner 

 just described. In the figure the great nocturnal rise and 

 the morning fall are greatly abbreviated, from the want of 

 space, and are merely represented by a short curved line. The 

 leaflet stood horizontally when at a point a little beneath the 

 middle of the diagram; so that during the daytime it oscillated 

 almost equally above and beneath a horizontal position. At 

 8.30 A.M. it stood 48° beneath the horizon, and by 11.30 a.m. it 

 had risen 50° above the horizon ; so that it passed through 98° 

 in 3 h. By the aid of the tracing we ascertained that the 

 distance travelled in the 3 h. by the apex of this leaflet was 

 1'03 inch. If we look at the figure, and prolong upwards in 

 our mind's eye the short curved broken line, which repre- 

 srnts the nocturnal course, we see that the latter movement is 

 merely an exaggeration or prolongation of one of the diurnal 

 ellipses. The same leaflet had been observed on the previous 

 day, and the course then pursued was almost identically the 

 same as that here described. 



* 'Flora,' 18i:3, p. 497. 



t ' Die Period. Bewegungen,' 1875, pp. 35, 52. 



