32 Newcombe, Sensitive Life of Asparagus ptumosus. 



have bent too for away from tlie eords to grasp them. The tips 

 are now tied back to the cords. Thirty hours later bot.h tips were 

 found twining, one having made 2 turns, the othcr 3 and one-half 

 turns abouth the cords. Et is evident thcrcfore that the shoots 

 wcre circunmutating yesterday, and began twining as soon as tied 

 in position to do so. Possibly they would have twined the day 

 betöre if they had been in proper position. 



Discussion. 



In the following discussion little tinie need be given to the 

 consideration of the various activities of Asparagus plumosus which 

 are similar to those of most orthotropic shoots. By reference to 

 the experimental part of this paper, it will be seen that the aerial 

 shoots of this plant, tili they reach a night of 10 cm to 30 cm, 

 are negatively geotropic and positively heliotropic, as are most 

 plants. At least the extent of this study has not discovered im- 

 portant differences. The negative thermotropism of the shoots has 

 been observed but not followcd in detail. 1t is the peculiar 

 behavior of this plant in turning the upper part of its aerial shoot 

 to the horizontal, as does Tropaeolum and Hedera heli>\ that will 

 here reeeive our chief attention. 



I. Cause of Plagiotropic Position. 



In Miss Conover's 1 ) paper, already referred to, very good 

 evidence w^as given for regarding the plagiotropic position as due 

 to diageotropism. This evidence, with my own added may be 

 summarized here: 



The plagiotropic declination is not due to negative heliotropism; 

 for, in the first place, the shoot remains positively heliotropic while 

 it is bending and after it has reached the horizontal position; and, 

 in the second place, seedlings raised in the dark will go to the 

 horizontal position, and shoots always in the dark, grown from 

 rhizomes, will decline toward the horizontal. 



The plagiotropic declination is not due to photonasty, for the 

 same reasons as given in the last paragraph. 



The plagiotropic position is not due to geonasty. The usual 

 fest for geonasty is made by inverting the plant so as to bring 

 the formerly upper side of the shoot below; or the formerly upper 

 side of the plagiotropic shoot is put in the flank position. The 

 convex side of the curve should then become still niore convex, 

 on the supposition that the resistance of geotropism is removed 

 by this change of position. This test, made for Asparagus, has 

 given no indication that the plagiotropic curve in this plant is 

 geonastic. Moreover, Miss Conover found by revolving a plant 

 on the horizontal klinostat, the orthotropic part of the shoot being 

 horizontal and the plant having recently made the plagiotropic 



l ) Conover, Behavior of Asparagus plumosus toward Gravitation and 

 Light. (Plant World. XVI. 1913.) 



