The
pollen thus collected lies close beneath the stigma, but can seldom gain
access into its cavity, except by the aid of insects, which pass their
proboscides down this passage into the nectary. (4/5. The flowers of
this plant have been fully described by Sprengel, Hildebrand, Delpino,
and H. Muller. The latter author sums up all the previous observations
in his 'Befruchtung der Blumen' and in 'Nature' November 20, 1873 page
44. See also Mr. A.W. Bennett in 'Nature' May 15, 1873 page 50 and some
remarks by Mr. Kitchener ibid page 143. The facts which follow on the
effects of covering up a plant of V. tricolor have been quoted by Sir J.
Lubbock in his 'British Wild Flowers' etc. page 62.) Consequently when I
covered up a large plant of a cultivated variety, it set only eighteen
capsules, and most of these contained very few good seeds--several from
only one to three; whereas an equally fine uncovered plant of the same
variety, growing close by, produced 105 fine capsules. The few flowers
which produce capsules when insects are excluded, are perhaps fertilised
by the curling inwards of the petals as their wither, for by this means
pollen-grains adhering to the papillae might be inserted into the cavity
of the stigma. But it is more probable that their fertilisation is
effected, as Mr. Bennett suggests, by Thrips and certain minute beetles
which haunt the flowers, and which cannot be excluded by any net.
Pages:
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196