27(J MODIFIED CIECUMNUTATION. Chap. V. 



and in -liued positions of the parts of plants* will see how diffi- 

 cult a subject this is, and will feel uo surprise at our expressing 

 ourselves doubtfully in this and other such cases. 



A plant, 20 inches in height, was secured to a stick close 

 beneath the curved summit, which formed rather less than a 

 rectangle with the stem below. The shoot pointed away from the 

 observer ; and a glass filament pointing towards the vertical glass 

 on which the tracing was made, was fixed to the convex surface of 

 the curved portion. Therefore the descending lines in the figure 

 represent the straightening of the curved portion as it grew 

 older. The tracing (Fig. 123, p. 274) was begun at 9 a.m. on 

 July 10th ; the filament at first moved but little in a zigzag line, 

 but at 2 P.M. it began rising and continued to do so till 9 p.m. ; 

 and this proves that the terminal portion was being more bent 

 downwards. After 9 p.m. on the 10th an opposite movement 

 commenced, and the curved portion began to straighten itself, 

 «nd this continued till 11.10 a.m. on the 12th, but was interrupted 

 by some small oscillations and zigzags, showing movement in 

 different directions. After 11.10 a.m. on the 12th this part of 

 the stem, still considerably curved, circumnutated in a con- 

 spicuous manner until nearly 3 p.m. on the 13th; but during all 

 this time a downward movement of the filament prevailed, 

 caused by the continued straightening of the stem. By the 

 afternoon of the 13th, the summit, which had originally been 

 defiected more than a right angle from the perpendicular, had 

 grown so nearly straight that the tracing could no longer be 

 continued on the vertical glass. There can therefore be no 

 doubt that the straightening of the abruptly curved portion of 

 the growing stem of this plant, which appears to be wholly due 

 to hyponasty, is the result of modified circumnutation. We 

 will only add that a filament was fixed in a different manner 

 across the curved summit of another plant, and the. same general 

 kind of movement was observed. 



TrifuKum repens. — In many, but not in all the species of Tri- 

 folium, as the separate little flowers wither, the sub-peduncles 

 bend downwards, so as to depend parallel to the upper part of 

 the main peduncle. In Tr. subterranettm the main peduncle 

 curves downwards for the sake of burying its capsules, and in 

 this species the sub-peduncles of the separate flowers bend 



* ' Ueber Orthotrope und Pla- ten des Bot. Inst., in WUrzburg,' 

 giotrope Pflanzentheile ;' 'Aibei- Heft ii. 1879, p. 226. 



