1898] NUTATION OF HELIANTHUS ANNUUS 401 
EFFECTS OF DECAPITATION, DEFOLIATION AND WOUNDING. 
In order to determine through what organs the stimulus was 
received which caused the stems to bend, the terminal buds of a 
large number of plants were removed, and it was found that this 
treatment had no effect whatever, at least no noticeable effect, 
on the daily nutation. The decapitated plants acted in the same 
way as others not thus treated, nutating from 40° to 60° in the 
morning and from 60° to go° in the evening. When conditions 
were favorable the decapitated plants nutated 90° west in the 
evening both on the day on which the operation was performed 
and for any number of days afterward. 
Plants were also wounded by cutting slices from the side of 
the stem midway between the terminal bud and the central point 
of curvature, both on the east side and on the west. But this 
seemed to have no more effect on the nutation than would fol- 
low from the mechanical interference caused by the wound. 
Plants were next treated by cutting off the leaves. In some 
the leaves were cut close to the stem, while in others the lamine 
Were cut off, the petiole being left. Plants thus treated immedi- 
ately lost their power of nutation. They would stand perfectly 
Upright, while their neighbors not so treated would nutate 90°. 
Some delaminated in the evening were found to be still inclining 
toward the west in the morning, while others had regained the 
upright position. When the leaves were cut in the morning the 
Plants were found to be perfectly upright in the evening, while 
the natural ones and some decapitated the same morning nutated 
90° west, 
Thus it appears that decapitation has no € 
Wounding the side of the stem affects nutation only to phe 
*xtent that it produces mechanical interference. Delamination, 
Whether of the blade or of the entire leaf, stops nutation entirely. 
It was Observed in some plants which had been delaminated 
that after the leaves and stems of the terminal bud had grown 
Slt again nutation was coritinued in the new parts, but nae 
bending was confined to those parts and did not extend below. 
ffect on nutation. 
