568 
ply of nourishment is scanty,—when the plant is 
starved and death is threatened,—the repro- 
ductive energies act with readiness, and flowers 
and seeds are freely produced. In other words, 
the scantier the supply of nourishment, the ear- 
lier will a plant propagate its kind. Hence seeds 
which are new or fresh produce plants with more 
luxuriant foliage, and less inclined to run into 
flower and fruit, than such as have been kept 
for some time and are partially spoiled. Pease, 
for example, are well known to be apt to run to 
straw where the ground is rich or moist; so that 
the employment of old ones for seed is, in such 
cases, the only suitable remedy. But where 
luxuriance of leaf and great size are the objects 
sought in any species of garden or farm produce, 
the newest and most vigorous seeds are eminently 
suitable,—especially, for example, with turnips 
and cabbage ; old seed producing plants too much 
disposed to run to flower. The law we have 
mentioned operates also on the growing plant 
itself; and occasions a variety of practices in 
horticulture which, though obviously depending 
on it, are in general but imperfectly understood 
by the practical gardener. The transplanting of 
fruit-trees, for instance, hastens the production 
of flower-buds. A tree which for years has shown 
no tendency to produce flower-buds, but which 
has been exclusively occupied in the extension 
of its roots and branches, will, upon being shifted 
from its place, soon exhibit symptoms of a change. 
The roots by this process have been in part in- 
jured, the supply of sap to the tree during the 
following season has in consequence become di- 
minished, and the plant, ceasing in a great mea- 
sure to increase its size, hastens to propagate its 
kind, by the production of flower-buds, and the 
subsequent display of blossoms and fruit. Again, 
when a rank growing fruit-tree is engrafted on 
a slow growing stock, or, in other words, when a 
tree requiring much sap is compelled to receive 
its supply through a tree having but a scanty 
supply, the engrafted branch will come earlier 
into fruit than if it had always been supplied 
with abundant nourishment; and this method 
of accelerating the production of fruit, and 
termed ‘dwarfing, is particularly serviceable in 
enabling the cultivator of new varieties to become 
early acquainted with their respective merits. 
When fruit-trees are prone to run to wood, gar- 
deners are accustomed to lay bare a portion of 
their roots during winter; and thereby many of 
their fibres are destroyed, and the vigour of all 
greatly diminished; so that the sap during the 
following summer is transmitted to the branches 
in less quantity, and the production of fruit-buds 
is the consequence. In the cultivation of flower- 
ing plants, a knowledge of this law and its ex- 
tensive application may prove of great impor- 
tance. Sir James Edward Smith, in his Intro- 
duction to Botany, mentions that the Solandra 
grandiflora, a Jamaica shrub, was for a number 
of years cultivated in the English stoves, and 
VEGETABLE PHYSIOLOGY. 
propagated extensively by cuttings, each ‘plant 
growing many feet in length every season, from 
the abundance of moisture and nourishment, 
without showing any signs of fructification. At 
length a pot of it was accidentally left without 
water in the dry stove at Kew; and, in conse- 
quence of this unintentional neglect, the luxu- 
riant growth of its branches was greatly checked, 
and a flower came forth at the extremity of each. 
By a similar mode of treatment, the same effect 
has since been frequently produced; and when 
the law is once properly understood, its appli- 
cation to a variety of cultivated plants, which 
are slow in showing flower, must be obvious. In 
the ordinary cultivation of farms, also, numerous 
examples of it are frequently occurring. The 
crops growing on the thinnest parts of the soil, 
where the nourishment is consequently dimin- 
ished, are always the first to exhibit their 
flowers, and to be ready for the sickle; and on 
ill-managed farms, the harvest is usually much 
earlier, other things being equal, than in those 
where the crops are under the influence of a 
better system. In the management of planta- 
tions, the indications of this law may often prove 
of great value; for wherever we see a tree, ina 
very young state, exhibiting its flowers and pro- 
ducing fruit, we may anticipate its early decay. 
The premature formation of fruit-buds is the 
consequence of a scanty supply of nourishment, 
arising, it may be, from the roots having been in- 
jured, but generally from the plant being placed in | 
an unfavourable soil. The balsam fir, for example, 
which thrives well on a moist soil, will, if planted 
ona thin dry soil, begin in a few years to produce 
cones,— then the bark appears covered with 
blisters which, when opened, pour forth a limpid 
resin, and the tree, after languishing a few years, 
dies. In looking at those decorated villas near 
a large town, which to the citizen appear so 
captivating, one may frequently discover the 
real character of the soil by the premature flow- 
ering of the ornamental shrubbery. 
The effect of gravitation on the growth and 
habit of plants, has been the subject of profound 
speculations and ingenious experiments, on the 
part of some of the most distinguished phytolo- 
gists; and, though probably over-estimated or 
confounded with other effects by its principal 
advocates, seems to be not only real but power- 
ful. “It can scarcely have escaped the notice of 
the most inattentive observer of vegetation,” 
says Mr. Knight, “that in whatever position a 
seed is placed to germinate, its radicle invariably 
makes an effort to descend towards the centre of 
the earth, while the elongated germen takes pre- 
cisely the opposite direction; and it has been 
proved by Duhamel, that if a seed during its 
germination be frequently inverted, the points 
both of the radicle and germen will return to the 
first direction. Some naturalists have supposed 
these opposite effects to be produced by gravita- 
tion; and it is not difficult to conceive that the 
