Brown. Baillon asserts
'Adansonia' tome 2 1862 page 58, that with many plants the tubes are emitted
from pollen-grains which have not come into contact with the stigma; and that
they may be seen advancing horizontally through the air towards the stigma. I
have observed the emission of the tubes from the pollen-masses whilst still
within the anthers, in three widely distinct Orchidean genera namely Aceras,
Malaxis, and Neottia: see 'The Various Contrivances by which Orchids are
Fertilised' 2nd edition page 258.) It is, however, a wonderful sight to behold
the tubes directing themselves in a straight line to the stigma, when this is at
some little distance from the anthers. As soon as they reach the stigma or the
open passage leading into the ovarium, no doubt they penetrate it, guided by the
same means, whatever these may be, as in the case of ordinary flowers. I thought
that they might be guided by the avoidance of light: some pollen-grains of a
willow were therefore immersed in an extremely weak solution of honey, and the
vessel was placed so that the light entered only in one direction, laterally or
from below or from above, but the long tubes were in each case protruded in
every possible direction.
As cleistogamic flowers are completely closed they are necessarily self-
fertilised, not to mention the absence of any attraction to insects; and they
thus differ widely from the great majority of ordinary flowers.
Pages:
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450