)
CONCLUDING REMARKS ON CLEISTOGAMIC FLOWERS.
That these flowers owe their structure primarily to the arrested development of
perfect ones, we may infer from such cases as that of the lower rudimentary
petal in Viola being larger than the others, like the lower lip of the perfect
flower,--from a vestige of a spur in the cleistogamic flowers of Impatiens,--
from the ten stamens of Ononis being united into a tube,--and other such
structures. The same inference may be drawn from the occurrence, in some
instances, on the same plant of a series of gradations between the cleistogamic
and perfect flowers. But that the former owe their origin wholly to arrested
development is by no means the case; for various parts have been specially
modified, so as to aid in the self-fertilisation of the flowers, and as a
protection to the pollen; for instance, the hook-shaped pistil in Viola and in
some other genera, by which the stigma is brought close to the fertile anthers,-
-the rudimentary corolla of Specularia modified into a perfectly closed
tympanum, and the sheath of Monochoria modified into a closed sack,--the
excessively thin coats of the pollen-grains,--the anthers not being all equally
aborted, and other such cases. Moreover Mr. Bennett has shown that the buds of
the cleistogamic and perfect flowers of Impatiens differ at a very early period
of growth.
Pages:
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448