These bees
visited several flowers, and could hardly have failed to cross-fertilise
them. Hive-bees and other small kinds sometimes collect pollen from old
and already fertilised flowers, but this is of no account. The rarity of
the visits of efficient bees to this exotic plant is, I believe, the
chief cause of the varieties so seldom intercrossing. That a cross does
occasionally take place, as might be expected from what has just been
stated, is certain, from the recorded cases of the direct action of the
pollen of one variety on the seed-coats of another. (5/14. 'Variation of
Animals and Plants under Domestication' chapter 11 2nd edition volume 1
page 428.) The late Mr. Masters, who particularly attended to the
raising of new varieties of peas, was convinced that some of them had
originated from accidental crosses. But as such crosses are rare, the
old varieties would not often be thus deteriorated, more especially as
plants departing from the proper type are generally rejected by those
who collect seed for sale. There is another cause which probably tends
to render cross-fertilisation rare, namely, the early age at which the
pollen-tubes are exserted; eight flowers not fully expanded were
examined, and in seven of these the pollen-tubes were in this state; but
they had not as yet penetrated the stigma. Although so few insects visit
the flowers of the pea in this country or in North Germany, and although
the anthers seem here to open abnormally soon, it does not follow that
the species in its native country would be thus circumstanced.
Pages:
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251