New combe . — The Sensory Zone of Roots, 431 
jets of water to one side of the tip. Four seedlings of 
Helianthus were used, and all four roots responded with 
positive curves ; while fourteen seedlings of Brassica were 
used, of which six roots gave positive curves, two gave 
negative curves, and six remained neutral. This evidence was 
not conclusive. 
<^1 
Fig. 24 (I). Illustration of a prepara- (II). Illustration of a preparation to 
tion to determine the sensitiveness of determine the extent of the sensory 
the apex of the root. The glass-tube zone. In this preparation 15 mm. of 
with its seedling was fastened to a bar the 'apex of the root is covered, the 
of wood. The packing of cotton is lowest circle of wire serving to mark the 
not represented. The arrows indicate height at which the root-tip is to be 
the direction of the current of water. kept during the experiment. 
Better results were obtained by another method. This 
consisted in the employment of glass-tubes to shield all of 
the root, except the apex, from the action of a stream of 
water in which the lower part of the seedlings was immersed. 
Thin-walled glass-tubes with an inner diameter of 3 mm. 
were cut to suitable lengths, the roots and hypocotyls of the 
