1819.] Direction of the Radicle and Germen. 255 
influence of gravitation to give an inclination downward to the 
oint of the radicle.” 
Whether Mr. Knight takes this supposed fact entirely upon 
the credit of others, or whether he confirmed it by his own 
observation, I cannot positively decide ; though the parenthesis 
contained in the above quotation renders the former part of the 
alternative the most probable. There is no doubt that many 
naturalists have been of this opinion, particularly Du Hamel, 
who gives a minute account of the experiment by which he 
seemed to have ascertained the fact. Having passed several 
threads through the root of a plant, and noted the distances, he 
then immersed the root in water. The upper threads retained 
always their relative and original situation, and the lowest thread, 
which was placed within a few lines of the end, was the onl 
one that was carried down. Hence he concluded that the root 
is elongated merely by the extremity.* - 
Resting upon this high authority, | confess that I did till 
lately assume the fact without exammation. But the result of 
the following experiment will show that the opinion is still 
incorrect, in spite of all the authorities by which it has been 
backed. 
On Oct. 1, 1818, I sowed some tick beans in a small earthen 
pan filled with garden mould. 
On the 4th, the radicle of the most forward had protruded 
about 1th of an inch beyond the integuments, when I marked it 
with ink at the point, in the middle, and- at the base, as clear- 
ing the integuments ; so that the marks were about 4th of an. 
inch from each other. 
On the 5th, the radicle was 1th of an inch in length, and the 
marks nearly as before with regard to their relative distances, 
but removed evidently from the integuments, so as to admit of a 
fourth or additional mark again adjoining the integuments. The 
radicle, which was originally upright, was now bending down. 
On the 6th, the radicle was + an inch in length, the first mark 
being within two or three lines of the point ; the second at about 
ith of an inch from the first ; the third at about 1th of an inch 
from the second ; and the fourth at about 1th of an inch from 
the third ; as well as perceptibly removed from the integuments. 
On the 7th, the radicle was th of an inch in length. The 
first mark was still within two or three lines of the point; the 
second was at the distance of 1 of an inch from the first ; the 
third was at the distance of 1 of an inch from the second; and 
the fourth was at about the distance of 1th of an inch from the 
‘third, being but little more than its original distance, but 
removed to the distance of jth of an inch from the integuments. 
On the 8th, the radicle was one inch in length, the first mark 
being still near the apex ; the second at the distance of about 
* Phys. des Arb, lib. i. chap. v. 
