430 Spalding. — On the Traumatropic 
the radicles were held was not accurately determined, but 
could not have varied much from 95 0 C. The tips of the 
radicles were held obliquely against the hot glass for five 
seconds, and then were allowed to grow in water of the 
temperature of the room. Seventeen hours later seven of 
the ten were curved away from the side to which heat had 
been applied. Of the three remaining ones, one was slightly 
bent away, or was doubtful, and two were bent in another 
plane. 
Aerial Roots. 
8. Ten of the aerial roots of Anthurium sp. growing in the 
moist air of the conservatory were branded in the usual way 
on the sloping side of the tip. Twenty-four hours later seven 
of the ten were strongly deflected, two at about a right angle, 
as shown in Fig. 6 . 
Microscopic examination shows that the root-cap constitutes 
a comparatively small proportion of the tip of the root, and 
does not extend far enough back to cover the curved part. 
It is continuous with the epidermis, into which it insensibly 
passes, there being no plain line of demarcation. In another 
specimen the curved part of the root extends to a still greater 
distance, so that the mechanical action of the root-cap is in 
the present case entirely inadequate to explain the curvature. 
In Anthurium, differentiation of the tissues takes place at 
a very short distance from the extremity of the root. 
Tracheids were distinctly traced as far as /, Fig. 6 . The 
curvature in the present case, therefore, takes place in tissues 
already differentiated, but making a rather rapid growth. 
This last is indicated by measurements made in connexion 
with the following experiment : — 
9. Ten aerial roots belonging to the three species 
Anthurium achranthum , A. hybridum , and A. Veitchi An- 
dreanum , were branded. Twenty-four hours later seven of 
the ten were traumatropically curved, four of them very 
strongly. The three that remained straight were found not 
to have grown appreciably. Those that had become curved 
