56 D. P. Penhallow — Tendril Movements. 



emerges from the bud condition, and the mean ratio of increase 

 (to original length) would be as 1:1*14, showing that the ten- 

 dril practically doubles its length during the period of circum- 

 nutation. This, taken in connection with previous facts, has a 

 striking; significance. 



The movement of the arm is not the only motion to be ob- 

 served in the tendril as a whole. It does not require a very 

 critical inspection to show that the same torsion which is de- 

 veloped in the arm, is also produced as conspicuously in the 

 petiole from which it springs, and, as Miss Gr. E. Cooley* has 

 demonstrated, the torsion is associated with a well-defined cir- 

 cumnutation of the petiole, independently of the movements of 

 its arms.f By inserting a fine glass filament, with a blackened 

 bead at its end, into the extremity of the petiole between the 

 arms, she clearly showed that the resulting figure corresponds 

 closely with that of an arm, when the two were in the same 

 line of extension, but differed when the tendril arm turned off 

 at right angles to its petiole. 



From structural considerations, we felt also justified in con- 

 cluding that the leaf tip must perform a circumnutation similar 

 to that of the tendril itself. This Miss Cooley also demon- 

 strated to be a fact. ~By placing a board, similar to that used for 

 taking the motion of the tendrils, against a leaf having a diam- 

 eter of 12 cm and a petiole 22 cm long, a figure of twenty-six 

 changes of direction was obtained within the space of three 

 hours. The movement was found to be much slower and the 

 figure much smaller than in the case of the tendrils. This, how- 

 ever, would appear to be the case from theoretical considera- 

 tions alone, when we compare the structural features of the 

 two and also take into account the great difference in diameter. 

 The figure described by the nutating tip of the leaf was quite 

 regularly ellipsoidal, though the curve was retraced before 

 the ellipse was fully completed, thus showing another point 

 of similarity to the movement of the tendril. The figure ob- 

 tained was 8 cm long by 5'5 cm wide, and the movement of 

 the leaf appeared to be through the two ends and one side 

 of the ellipse. Whether this would hold true in all cases or 

 not, could only be determined from a greater number of obser- 

 vations. The important fact is demonstrated, however, that 

 the leaves have a definite circumnutation, and that this depends 

 upon the same causes which determine the movement of other 

 organs in the same plant. 



While experimenting with the tendrils, it was also deemed 

 advisable to determine the movements of the growing extrem- 



* Assistant Professor of Botany, Wellesly College. The facts collected by her 

 were obtained during a course of Physiological Botany under my direction, 

 f This is in harmony with the observations of Sachs. Text-book, p. 870. 



