112 TENDEIL-BEAKEES. Chap. Ill 



revolve in ellipses. The ellipses are generally very 

 narrow, but sometimes approach to circles. I several 

 times observed that the longer axis slowly changed its 

 direction, which is of importance, as the tendril thus 

 sweeps a wider space. Owing to this change of 

 direction, and likewise to the movement of the stem 

 towards the light, the successive irregular ellipses 

 generally form an irregular spire. I have thought it 

 worth while to annex a tracing of the course pursued 

 by the upper intemode (the movement of the tendril 

 being neglected) of a young plant from 8.40 A.M. to 9.15 

 P.M. The course was traced on a hemispherical glass 

 placed over the plant, and the dots with figures give 

 the hours of observation ; each dot being joined by a 

 straight line. No doubt all the lines would have been 

 curvilinear if the course had been observed at much 

 shorter intervals. The extremity of the petiole, from 

 which the young tendril arose, was two inches from 

 the glass, so that if a pencil two inches in length 

 could have been aflSxed to the petiole, it would have 

 traced the annexed figure on the under side of the 

 glass ; but it must be remembered that the figure is 

 reduced by one-half. Neglecting the first great 

 sweep towards the light from the figure 1 to 2, the 

 end of the petiole swept a space 4 inches across in one 

 direction, and 3 inches in another. As a full-grown 

 tendril is considerably above two inches in length, and 

 as the tendril itself bends and revolves in harmony 

 with the intemode, a considerably wider space is swept 

 than is here represented on a reduced scale, Dutrocbet 



