104 Newcombe, Gravitation sensiviteness not confined to apex of root. 
2 outward curves of 15« during a period of 6 hours. Two and 
a half miUimeters were cut from the tips of 45 roots and these 
seedlings as the others were revolved for seven and one-half hours 
at 7 g to 8 g. Among them, 13 roots curved outward at angles 
varying from 15*^ to 45 3 roots hent inward, and the remaining 
29 roots grew straight. 
These results may he accepted as demonstrating the ability 
of the beheaded roots of this species to respond to the centrifugal 
force, but the number of seedlings employed when 2 mm of the 
root were excised was too few to allow comparisons to be made 
with those from which 2.5 mm were removed. The large number 
of seedlings used when 2.5 mm were removed and the resulting large 
number of neutral roots makes certain the conclusion that, tho some 
individuals so treated are capable of responding, the large majority 
have lost that ability. 
Bicinus communis. Fifty-two seedlings with tips amputated 
Avere revolved on the centrifuge at 8 g, temperature 20 ® to 22»C, 
and period 6 to 8 houi’s. None of them showed curves that could 
be caUed geotropic. All of the roots grew straight except 10 
which curved but slightly in various directions. Twenty of these 
roots had 3 mm excised, 13 had 2.5 mm excised, 13 had 2 mm excised, 
and 6 had 1.5 mm excised. None of those in the last two groups 
showed any curvature. 
This species is distinguished as the only one of the seven used 
inthiswork which does not respond to centrifugal action when 1.5 to 
2 mm of the root are removed. 
Vida faba. The response of the roots of this seedling onthe 
centrifuge was determined by Wiesner as possible but infre¬ 
quent when 3 mm were amputated. In my experiments a beginning 
was made by amputating 2.5 mm, and subjecting the seedlings to a 
speed of 8 g in temperature varying from 20 ^ to 23 ^ C. Fourteen 
seedlings were revolved during 7 hours, and 8 curved outward at 
angles ranging from 15 ® to 66 one curved toward the center and 
five grew straight. 
A\Tien under the same conditions 41 seedlings were used 
from which 3 mm of the root had been removed, 34 made 
outward curves at angles ranging from 15 ® to 50 averaging 
over 30 o; only one root curved inward, while the other 6 
grew straight. 
Forty roots had 3.5 mm of the tip removed, Avere revolved 
at 8 g, in a temperature generally of 21 (for one set of 4 roots 
it was only 14 ^ C, but the period here was lengthened to 10 
hours), for a period of 6 to 8 hours. Twenty-six roots bent out¬ 
ward, one inward, 3 obüquely t^ the plane of revolution, and 10 
grew straight. The angles formed by these roots averaged slight¬ 
ly less than those formed by the roots Avhich had but 3 mm am¬ 
putated. See Plate TU for one set of these seedlings. 
Thirty-five roots had each 4 mm removed from the tip, 
were revolved at 8 g, temperature was 20 ® to 23 and the period 
6 so 7 hours. Sixteen roots bent outward, and 19 grew straight, 
