BUD VARIATION. 
253 
A similar precaution is exercised by gardeners in the case of 
fruit-tree grafts. 
The different forms which plants assume at different stages 
of their existence under normal circumstances must also be 
taken into consideration in speculating on the origin of bud 
variation. A large number of plants do not immediately 
assume their wonted habit, they pass through an intermediate 
stage or stages. This is particularly observable in the case of 
Conifers, the juvenile state of which is often very different from 
the appearance presented in the adult state. It now and then 
happens that, after a plant has lost its youthful characters 
and assumed its full-grown developement, sundry branches, 
for some unknown reason, revert to the infantile form. In the 
common ivy we have a familiar illustration of a similar 
phenomenon. When the plant is about to produce flowers it 
assumes an erect bushy habit, its leaves alter in form, indeed 
its whole aspect becomes changed. If now such branches be 
taken off and propagated, the characteristic form remains as in 
what are called tree ivies. If the life history of such a plant 
were not known, the bud variation just mentioned would appear 
even more inexplicable than it now does. Again, the leaves 
and flowers produced on the same plant at different seasons are 
often naturally different. Dr. Balfour has lately called atten- 
tion to a remarkable instance of this phenomenon in a species 
of hawkweed, Hieracium , which presents three distinct forms 
according to the season at which it flowers. Occasionally even 
a casual observer is struck by the appearance of a second or 
even a third crop of flowers on laburnums, or pear-trees, Wist- 
arias, and others. In such instances it will generally be found 
on examination that the adventitious flowers spring from buds 
which under ordinary circumstances never produce flowers, but 
only leaves, or that they are placed on portions of the tree 
usually devoted solely to the production of leaves. How much 
the aspect of the tree is altered in such cases may readily be 
surmised : the casual spectator cannot fail to notice it, but the 
explanation of the phenomenon rarely strikes him. 
As might have been anticipated, a change in the external 
conditions under which a plant lives will often cause very con- 
siderable variation in its form : thus a species of fig, Ficus 
stipulata , is commonly grown on the walls of hot-houses, to- 
which it clings ivy-fashion. The same plant grown as a standard 
in a pot has a totally different appearance. On the wall it 
has small thin leaves, and it clings to its surface like a large 
moss or a miniature ivy. Planted out it forms a stout bushy 
shrub with large coarse leathery leaves, so different from those 
formed when the plant is growing against a wall that no 
botanist unacquainted with the history of the plant would 
