;',(') Newcombe, Sensitive Life of Asparagus plumosus. 



this alternate declension and erection of the tip continues as long 

 as fche shoot continues to grow in the dark, which may last for 

 several inonths. This declension and erection of the tip is not 

 mere ephemeral nutation. I conld not see that Asparagus increased 

 its ephemeral nutation in the dark, as Maige 1 ) found to be true 

 for Stachys palustris and Mentha arvensis. Each of the larger 

 dcclinations that the tip took was immediately controlled by gravi- 

 tation as was demonstrated several tinies by displacing the shoots 

 from that position, and noting their quick return. There were also 

 positions, divergent from the vertical, assumed often for but brief 

 periods, an hour, more or less. Whether in such a case plagio- 

 geotropisin had taken the tip to its position, i had no means of 

 determining, except to remember that on the horizontal klinostat 

 in the dark such nutation did not take place. 



By reference to that part of this paper entitled, „Behavior 

 of Shoots exposed to Light for One to Several Days", it will be 

 seen that the effect of light on the assumption and retention of 

 the diageotropic position makes itself feit at a distance of several 

 days, 8 days at least. This is evidenced from the fact that those 

 shoots which were covered from the light 8 days, or less, before 

 they made the plagiogeotropic decline, retained the plagiotropic 

 position permanently and unfolded their branches. Other shoots 

 which were covered for a longer time before they made the decline, 

 11 days or more, probably would have erected later, but the ex- 

 periments were not continued long enough to determine. But 

 since the branches had not begun to unfold, it may be inferred 

 that the shoot had not come to its definitive growth. Both in the 

 normally growing plants and in those growing in the dark, the 

 beginning of the unfolding of the branches was a sign that elon- 

 gation of the main axis was about to end. The formation of the 

 plagiotropic curve is thus a phase phenomenon, related to the phy- 

 siological State, related to the approaching cessation of growth. 

 Apparently, on the withdrawal of light, the inhibition of growth 

 is removed and there arises a contest within the plant itself, on 

 the one hand, for ending growth and making the plagiotropic curve, 

 and, on the other, for continuing growth. Temporarily one tendency 

 gains the ascendency and temporarily the other, and thus the 

 contest goes on indefinitely, but with the end-result favorable to 

 growth; for the orthotropic elongation of the shoot in the dark is 

 far in excess of the plagiotropic. In the case of seedlings, the 

 exhaustion of stored food entails the cessation of growth in the 

 dark. Whether the seedling shoots would make the plagiotropic 

 bend in the dark, were there a continuing supply of food, we have 

 no means of knowing. 



That light bears some part in bringing the aerial shoot growing 

 from the rhizome to the füll diageotropic position, thru changing 

 the response to gravitation is illustrated by the behavior of such 



a 



*) Maige, Recherches sur les plantes rampantes. (Ann. Sei. Nat. Sei*. 8. 

 VII. 1900. p. 249.) 



