230 AUTONOMOUS MOVEMENTS. [CH. VIII 



of the stem should project beyond the upper end of the 

 stick and hang over so as to be more or less horizontal. If 

 the flower-pot stands on a sheet of paper it is easy to note, 

 by means of a line drawn radially from the pot as a centre, 

 the direction in which the nutating shoot points at any 

 moment ; and thus the rate at which it swings round can 

 be recorded. One revolution in 2 hours is what may be 

 expected in a vigorous plant. Note that the hop travels 

 with the hands of a watch, Phaseolus against it : also, that 

 if they are allowed to climb up sticks they do so by 

 an apparent continuation of their revolving nutation. 

 Thus a hop which has wound spirally round a support 

 makes a left-handed screw, while Phaseolus is right- 

 handed. 



(260) Autonomous movements: Trifolium. 



The spontaneous variation-movements of leaves may 

 easily be studied in the genus Trifolium 1 . They may 

 be observed by a modification of the method described 

 in exp. 258, or by Pfeffer's method, which is simpler and 

 on the whole gives more reliable results. Transplant a 

 lump of turf, containing a plant of clover, to a flower-pot : 

 fix a vertical stick (about as thick as a pencil) firmly into 

 the soil and attach the petiole of a leaf to it by two bands 

 of gummed paper so that the top of the petiole is level 

 with the top of the stick. The terminal leaflet is free to 

 move, and its movements are observed by fixing with 

 shellac- varnish a very fine glass filament along the midrib 

 on the upper surface so as to project 2 or 3 mm. Cut out 

 1 See Sachs' Physiologic (French Trans.), p. 515. 



