n; Newcombe, Sensitive Life of Asparagua pUtmosUS. 



experiments. Moreover, the main axis and thc larger branches 



are positively heliotropic after both of these have taken the hori- 

 zontal position. as has bcen seen many times in one-sided illiunination. 

 The lateral branches of all Orders seem to be froin the be- 

 ginning of their unfolding diageotropic. They do not begin to 

 unfold tili the main axis is near the end of its growth, and they 

 have never been seen to assuine the vertical position even tem- 

 porarily. Since the lateral branches of all Orders before they start 

 unfolding- lie appressed and parallel with the axis that bears thern, 

 and since, in the non-twining shoots, the main axis goes to the 

 horizontal position before the lateral branches begin to unfold, it 

 follows that these horizontal branches are already in the horizontal 

 position when they begin unfolding. The shifting of position by 

 these branches by which they come, all except the needles, to 

 extend nearly at right angles to the respective axes which bear 

 them, is therefore not due to diageotropic respose, but must come 

 froni internal Stimulation which causes each nember, in the language 

 of science, to assume its "proper angle". The needles, whether 

 borne on main axis or a brauch of any Order, spread out in a 

 horizontal layer like the spokes of a wheel, often Alling a complete 

 circle, but more often connning themselves to a semicircle. It is 

 evident that the diageotropism of all of the horizontal members 

 determines their horizontal position, but internal Stimulation de- 

 termines the position the branches shall occupy in this horizontal 

 plane with respect to one another and to the main axis. So strong 

 is this respanse to internal Stimulation that a shoot which has 

 taken the horizontal position and is placed parallel to a window 

 with one-sided illumination will unfold its branches to the right 

 and left of the main axis almost unaffected by the direction of 

 light. That is to say, if we imagine a vertical plane to pass thru 

 the axis of the horizontal shoot subjected to one-sided illumination, 

 so that one side of the vertical plane is shaded and the other 

 illuminated, we might expect that an unfolding brauch which has 

 its origin, say only 10° to the shaded side of the vertical plane, 

 would bend across the vertical and place itself on the illuminated 

 side. This result, however, does not follow in the experiment, 

 but the branch Swings out on the shaded side. 



As pointed out by Miss Conover 1 ), the diageotropic shoots 

 when still in a plastic condition make no effort to reverse whcn 

 the plant is inverted; rior does main axis or brances twist thru an 

 angle of 90° if the plane of the flanks of the horizontal members 

 is revolved thru 90° about the horizontal axis. This result can 

 niean nothing less than that the diageotropic members are radial 

 and not dorsiventral as far as behavior is concerned. Structurally 

 also, there is no evidence of dorsiventrality. 



A young orthotropic shoot, revolved on the klinostat tili 

 grown to maturity, retains its orthotropic habit and retains also 



J ) Conover, Behavior of Aspuragus plumosus howanl Gravitation and 

 Light. (Plant World. XVI. 1913.) 



