Curvature of Roots . 433 
but after some practice can readily be performed, at least to 
the extent of making sure that no more than a very insig- 
nificant part of the root-cap remains. After the removal of 
the root-cap the tips were branded in the usual way and the 
radicles allowed to grow in water. Twenty-three hours later 
seven of the ten radicles were strongly deflected. Of the 
remaining three, one was slightly deflected, one was straight, 
and one was slightly curved towards the branded side. The 
appearance of the seven was so striking that there could be 
no hesitation in pronouncing this a plain case of traumatropic 
curvature. Microscopical examination showed that all of 
the thicker part of the root-cap was removed, or was subse- 
quently killed by branding. There is absolutely no reason to 
suppose that the extremely small amount of tissue remaining 
as root-cap is the active agent in bringing about curvature. 
15. Twenty healthy specimens of Vicia Faba with radicles 
varying in length from 2 to 4*5 cm. were cut, or stabbed, with 
a sharp-pointed lancet, without removing any of the tissue of 
the root-cap. 
(a) Ten were cut close to the apex in a tangential 
direction, care being taken to make the cut as shallow as 
possible, so that it was certain that only tissues of the root- 
cap were wounded. 
(b) Six were cut in the same way, but much deeper, so 
as to make sure of wounding the tissue of the growing-point, 
the instrument still being held tangentially. 
( c ) Four were also wounded deeply, but the instrument 
in this case was held radially, so as to disturb the tissue 
of the root-cap as little as possible, though it must never- 
theless result in cutting a considerable amount of tissue both 
in the root-cap and in the growing-point. 
An examination of these different lots, five hours later, 
showed that of the first lot of ten specimens, five were de- 
flected ; of the second lot of six specimens, five were deflected, 
and the sixth probably also, but doubtful ; and of the third 
lot of four, three were deflected, the fourth being doubtful. 
Comparing the three lots and noting amount of curvature 
