so common occurrence as the
change above alluded to, but by the art of the gardener the change is
often effected. In rhododendrons and in peach trees and roses I have met
with this change occurring without human agency. The means adopted by
the gardener are such as check the luxuriance of the leaf-shoots,[173]
and this is effected in various ways, as by continuous "pinching" or
removal of the leaf-buds, by pruning, ringing the bark, confining the
roots, limiting the supply of nutriment, and other means all based on
the same principle. Some of the Cape bulbs (_Cyrtanthus_) are known not
to produce their flowers till their leaves have received, in some
manner, a check. Fires which often destroy the herbage thus have the
effect of throwing the plant into bloom. A very remarkable instance is
recorded of the production of flower-buds after an injury to the
leaf-buds in the 'Bulletin of the Botanical Society of France,' vol. ix,
p. 146. It appears that during the war of the French against the Arabs
in Algiers, the latter planted several hundreds of Agaves with a view to
obstruct the passage of the French cavalry. The soldiers hacked these
plants with their sabres, and cut out the central tuft of leaves, or the
heart, as gardeners call it. The following season almost every one of
these Agaves sent up their large handsome flower-spikes. It is well
known that, under ordinary circumstances, these plants do not flower
except at long intervals of time.

=Presence of flowers on spines.=--That the spine, as a contracted
branch, should occasionally produce flowers is not to be wondered at,
though the occurrence is by no means common. M. Baillon showed at a
meeting of the Botanical Society of France ('Bulletin,' vol. v, 1858, p.
316) a branched spine of _Gleditschia_ bearing a flower at the end of
each of the sub divisions. This was, therefore, strictly analogous with
those cases in which the peduncle is normally spiney.

=Formation of flower-bud on the petals.=--An instance of this, it is
believed, the only one on record, is cited in the 'Gardeners' Chronicle'
for 1865, p. 760, by the Rev. M. J. Berkeley, who describes the
formation of a flower-bud on the surface of a petal of _Clarkia
elegans_. Reasoning from analogy there seems no reason why buds should
not be formed on the petals as well as on the leaves.

=Formation of buds on fruits.=--This is a point of some moment with
reference to the share which the axis takes in the produ