New combe, — The Sensory Zone of Roots . 439 
Helianthus annuus> L., like F agopyrum esculentum , does 
not produce all its roots straight in water. It is a plant 
giving 70 per cent, of positive rheotropic curvatures when 
the naked roots are acted on by a stream of water, but the 
angles attained average less than 45 0 . This behaviour places 
this plant among those with a good degree of sensitiveness 
to a stream of water, but considerably below the grade of 
Raphanus and Brassica. The following table will show that, 
like Fagopyrum , this plant gives a considerable number of 
negative bends, which are to be interpreted as merely the 
result of the environment of water. 
Table IV. Helianthus annuus with root-tips shielded 
from the water-stream by glass-tubes. Temperature of the 
water = 24 ; duration of the experiments = 11 hours ; velocities 
— from 200 cm. to 700 cm. per minute. 
No. 
Seedlings. 
Extent of 
Apex shielded. 
Positive Curves . 
Neutral Roots. 
Negative Curves. 
30 
10 mm. 
22 = 73% 
6 
2 
46 
15 mm. 
23 = 50 % 
14 
9 
29 
20 mm. 
u = 38% 
14 
4 
32 
25 mm. 
11 = 34 % 
15 
6 
The results of individual experiments carried through on 
various days agree very closely with the proportions shown in 
the totals of the table. For those roots with 10 mm. shielded, 
two experiments were made with fifteen seedlings in each. 
Each experiment gave eleven positive curves, while one 
experiment gave two negative curves and two neutral roots, 
and the other gave no negative curves, but four neutral roots. 
The experiments with 15 mm. of the root covered numbered 
four. The first one of these four sets of roots had eight 
individuals, and gave three positive curves, three negative, 
and two neutral roots ; the second had fourteen individuals, 
and gave seven positive curves, two negative, and five neutral 
roots ; the third set had twelve individuals, and gave seven 
