Another kind of gradation well deserves notice. Flower-tendrils (B,
fig. 10) sometimes produce a few flower-buds. For instance, on a
vine growing against my house, there were thirteen and twenty-two
flower-buds respectively on two flower-tendrils, which still retained
their characteristic qualities of sensitiveness and spontaneous
movement, but in a somewhat lessened degree. On vines in hothouses,
so many flowers are occasionally produced on the flower-tendrils that
a double bunch of grapes is the result; and this is technically
called by gardeners a "cluster." In this state the whole bunch of
flowers presents scarcely any resemblance to a tendril; and, judging
from the facts already given, it would probably possess little power
of clasping a support, or of spontaneous movement. Such flower-
stalks closely resemble in structure those borne by Cissus. This
genus, belonging to the same family of the Vitaceae, produces well-
developed tendrils and ordinary bunches of flowers; but there are no
gradations between the two states. If the genus Vitis had been
unknown, the boldest believer in the modification of species would
never have surmised that the same individual plant, at the same
period of growth, would have yielded every possible gradation between
ordinary flower-stalks for the support of the flowers and fruit, and
tendrils used exclusively for climbing.
Pages:
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185