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possesses, we must assume that some kind of heliotropism enters into the 
combination. 
The view to which the present research lends most probability is, that dia- 
heliotropism (transverse-heliotropism) is the really important influence at 
work. In the case of the celandine we have seen that the sensitiveness to 
light is strong enough to determine the position of the leaves, although the 
natural balance is disturbed by the annihilation of geotropism. It seems 
probable that an essentially similar state of things holds good in the case of 
the cherry. When the plant is growing normally, it trusts to epinasty and 
apogeotropism to produce an approximate balance, the final result being 
determined by the stimulus of light ; but when the balance is disturbed by 
placing the plant on the clinostat, the light-stimulus is not strong enough to 
produce a condition of equilibrium. 
This view is the same as that given in The Tower of Movement in Plants , 
and is in accordance with the principle there laid down, — that the chief 
movements in plants are due to modifications of the circumnutatory motion. 
II. When a cutting — for instance, a piece of a willow-branch — is placed 
in circumstances favourable for growth, it produces roots at its lower end, 
while the buds at its upper end grow out into branches. The experiments of 
Vochting * on the growth of cuttings were made by suspending pieces of 
stems and branches, &c. in large, darkened jars, the air in which was kept 
constantly moist by a lining of wet filter-paper. The cuttings were suspended 
both in the normal position, that is, with the upper end upwards, and also 
upside down. Vochting found, as a general result, that there is a strong 
tendency for the roots to appear at the basal end, t and the branches to be 
developed at the apical end, whether the cutting had been hung apex up- 
wards or downwards in the glass jar. 
Vochting believes that the growth of roots at the base, and of branches 
at the apex of a cutting, is determined chiefly by an innate inherited 
growth-tendency. When the knife divides a branch into two cuttings, it 
separates a mass of identically constituted cells into two sets ; one forming 
part of the apex of the lower cutting, and another set which forms part 
of the base of the upper cutting. And under appropriate circumstances one 
of these sets of cells might develope into roots, the other into adventitious 
buds. It is Vochting’s belief that the morphological positions of these 
sets of cells, the fact of one being at the base, and the other at the apex 
of a cutting, chiefly determines the course of their subsequent develop- 
ment. The idea may be expressed somewhat familiarly, by saying that 
each cutting into which a branch is divided is able to distinguish its base 
from its apex, and can tell where to produce the growth of roots and buds, 
by means of an internal impulse which is independent J of the external 
forces, gravitation and light. 
* Organbilduny im Pjlanzenreich. Bonn, 1878. 
t The basal is that end of a cutting nearest to the parent plant ; the 
apical end is the opposite end. 
\ Vochting states distinctly that gravitation and light do affect the 
positions in which organs are developed in cuttings, but he considers the 
internal impulse to be a stronger determining cause. 
