BEHAVIOR OF ASPARAGUS PLUMOSUS 



65 



of the youngest shoot bent back parallel with the axis of revo- 

 lution and grew toward the pot. The tips of the other two 

 shoots continued on in a straight course parallel with the axis 

 of revolution. All three tips, therefore, had placed themselves 

 at right angles to the direction of the "centrifugal force," which 

 corresponds to the diageotropic position. 



11. THE PRESENCE OF MORPHO-PHYSIOLOGICAL UPPER AND LOWER 

 SIDES TO THE HORIZONTAL PART OF THE SHOOT 



There can be no doubt that the position of equilibrium for 

 the apical portion of the mature shoot is diageotropic. "VMien 

 this position is assumed, the plant member may, hypotheti- 

 cally, still be radial or it may be dorsiventral. Moreover, 

 it may, to outward appearances, be morphologically radial and 

 physiologically dorsiventral. 



An examination of the external morphology shows no reason 

 for calling the horizontal portion of the shoot dorsiventral. 

 The following experiments show also that there is no physio- 

 logical dorsiventrality : 



Two pots of plants with altogether three orthotropic young 

 shoots were inverted and thus suspended from a rafter in the 

 greenhouse. The two older shoots soon bent into the hori- 

 zontal position. The third and youngest shoot bent upward, 

 .parallel with its own lower portion, proceded vertically upward 

 for a few centimeters, and then bent its apical 2 cm. into the 

 horizontal position. All three of these shoots turned the side 

 upward that would have been the lower side, had the plants 

 not been inverted. 



Two other pots each with a young shoot whose apex had 

 only a day before taken the horizontal position were laid on 

 their sides so that the bent apex of one of the young shoots 

 pointed vertically upward, while the apex of the other young 

 shoot was a little below the horizontal plane. After twenty- 

 five hours the tip that was directed vertically upward retained 

 its original bend, but turned its apex for a length of 2 cm. into 

 the horizontal position, the formerly lower side being now upper- 

 most. In the same time the tip of the second shoot had also 



