If these florets had opened for a short time unperceived by me and had then closed again, the empty anthers would have been left dangling outside. Nevertheless they yielded on August 17th an abundance of fine ripe seeds. Here then we have a near approach to the single case as yet known of this grass producing in a state of nature (in Germany) perfect flowers which yielded a copious supply of fruit. (8/26. Dr. Ascherson 'Botanische Zeitung' 1864 page 350.) Seeds from the cleistogamic flowers were sent by me to Mr. Scott in Calcutta, who there cultivated the plants in various ways, but they never produced perfect flowers.
In Europe Leersia oryzoides is the sole representative of its genus, and Duval- Jouve, after examining several exotic species, found that it apparently is the sole one which bears cleistogamic flowers. It ranges from Persia to North America, and specimens from Pennsylvania resembled the European ones in their concealed manner of fructification. There can therefore be little doubt that this plant generally propagates itself throughout an immense area by cleistogamic seeds, and that it can hardly ever be invigorated by cross- fertilisation. It resembles in this respect those plants which are now widely spread, though they increase solely by asexual generation. (8/27. I have collected several such cases in my 'Variation under Domestication' chapter 18 2nd edition volume 2 page 153.)
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.
The degree to which many of the most important organs in these degraded flowers have been reduced or even wholly obliterated, is one of their most remarkable peculiarities, reminding us of many parasitic animals. In some cases only a single anther is left, and this contains but few pollen-grains of diminished size; in other cases the stigma has disappeared, leaving a simple open passage into the ovarium. It is also interesting to note the complete loss of trifling points in the structure or functions of certain parts, which though of service to the perfect flowers, are of none to the cleistogamic; for instance the collecting hairs on the pistil of Specularia, the glands on the calyx of the Malpighiaceae, the nectar-secreting appendages to the lower stamens of Viola, the secretion of nectar by other parts, the emission of a sweet odour, and apparently the elasticity of the valves in the buried capsules of Viola odorata. We here see, as throughout nature, that as soon as any part or character becomes superfluous it tends sooner or later to disappear.
Another peculiarity in these flowers is that the pollen-grains generally emit their tubes whilst still enclosed within the anthers; but this is not so remarkable a fact as was formerly thought, when the case of Asclepias was alone known.