In the mid-styled form, the
stigma is placed rather above the middle of the corolla, and nearly on a level
with the mid-length stamens in the other two forms; its summit is a little bent
upwards. In the short-styled form the pistil is, as we have seen, very short,
and differs from that in the other two forms in being straight. It stands rather
beneath the level of the anthers of the shortest stamens in the long-styled and
mid-styled forms. The three anthers of each set of stamens, more especially
those of the shortest stamens, are placed one beneath the other, and the ends of
the filaments are bowed a little upwards, so that the pollen from all the
anthers would be effectively brushed off by the proboscis of a visiting insect.
The relative diameters of the pollen-grains, after having been long soaked in
water, are given in Table 4.d, as measured by my son Francis.
TABLE 4.d. Pontederia. Diameters of pollen-grains, after having been long soaked
in water, in divisions of the micrometer.
Column 1: Source of Pollen-grains.
Column 2: diameter.
Long-styled form, mid-length stamens (Average of 20 measurements): 13.2.
Long-styled form, shortest stamens (10 measurements): 9.0.
Mid-styled form, longest stamens (15 measurements) : 16.4.
Mid-styled form, shortest stamens (20 measurements): 9.1.
Short-styled form, longest stamens (20 measurements): 14.
Pages:
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255