These cases show how largely pollen from a
neighbouring variety of the cabbage effaces the action of the plant's
own pollen. We should bear in mind that pollen must be carried by the
bees from flower to flower on the same large branching stem much more
abundantly than from plant to plant; and in the case of plants the
flowers of which are in some degree dichogamous, those on the same stem
would be of different ages, and would thus be as ready for mutual
fertilisation as the flowers on distinct plants, were it not for the
prepotency of pollen from another variety. (10/36. A writer in the
'Gardeners' Chronicle' 1855 page 730, says that he planted a bed of
turnips (Brassica rapa) and of rape (B. napus) close together, and sowed
the seeds of the former. The result was that scarcely one seedling was
true to its kind, and several closely resembled rape.)
Several varieties of the radish (Raphanus sativus), which is moderately
self-fertile when insects are excluded, were in flower at the same time
in my garden. Seed was collected from one of them, and out of twenty-two
seedlings thus raised only twelve were true to their kind. (10/37.
Duhamel as quoted by Godron 'De l'Espece' tome 2 page 50, makes an
analogous statement with respect to this plant.)
The onion produces a large number of flowers, all crowded together into
a large globular head, each flower having six stamens; so that the
stigmas receive plenty of pollen from their own and the adjoining
anthers.
Pages:
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559