Among trees the pendulous or weeping, and the broomlike or fastigiate
forms are very marked varieties, which occur in species belonging to
quite different orders. The ash, the beach, some willows, many other
trees and some [136] finer species of garden-plants, as _Sophora
japonica_, have given rise to weeping varieties, and the yew-tree or
_Taxus_ has a fastigiate form which is much valued because of its
ascending branches and pyramidal habit. So it is with the pyramidal
varieties of oaks, elms, the bastard-acacia and some others.
It is generally acknowledged that these forms are to be considered as
varieties on the ground of their occurrence in so wide a range of
species, and because they always bear the same attributes. The pendulous
forms owe their peculiarity to a lengthening of the branches and a loss
of their habit of growing upwards; they are too weak to retain a
vertical position and the response to gravity, which is ordinarily the
cause of the upright growth, is lacking in them. As far as we know, the
cause of this weeping habit is the same in all instances. The fastigiate
trees and shrubs are a counterpart of the weeping forms. Here the
tendency to grow in a horizontal direction is lacking, and with it the
bilateral and symmetric structure of the branches has disappeared.
Pages:
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148