When that point is elapsed, the anthers have not any pollen, and modifications happen within the filaments the result of which is that the anthers now not occupy their former position. He had expressed this view earlier than in 1761; he repeated it in 1763 with the concept the male and female moistures unite together, as an acid and an alkali unite to type a impartial salt; a new dwelling organism is the outcome at once or later of this union. Now the spot, which was at first occupied by the ripe anthers and is now occupied by the ripe stigma, is so chosen in each flower, that the insect for which the flower is intended cannot attain the juice with out touching with a por tion of its body the anthers in a young flower, and the stigma in an older; it thus brushes the pollen from the anthers and conveys it to the stigma, and so the pollen of the younger flower fertilises the older.’ It has been already said, that Sprengel was additionally acquainted with the alternative form of dichogamy; and the result of his rationalization of both kinds is the conclusion, that some flowers can only be fertilised by the help of insects, and he adds that some circumstances are to be found, wherein the arrangements within the flower are of such a nature as to contain the injury and even the demise of the insect that provides its providers.
Sprengel set out with the thought, that the nectar and certain preparations in flowers are expressly meant for the service of insects; but his investigations led him finally to the conclusion, that insects themselves serve not only to effect the fertilisation of plants typically, but also in all strange instances to deliver about the crossing of different flowers of the same plant or of different plants of the identical species. As Camerarius first proved that plants possess sexuality, and Koelreuter showed that plants of various species can unite sexually and produce fruitful hybrids, so now Sprengel confirmed that a certain type of hybridisation is frequent within the vegetable kingdom, namely the crossing of different flowers or totally different individuals of the identical species. Gärtner rightly appealed to Koelreuter’s hybrids against the defenders of the theory of evolution; and to those who saw within the seed only another type of vegetative bud, he mentioned, that the bud can produce a brand new plant without fertilisation however that the seed can’t. Nevertheless he discovered that the outer covering of the pollen-grain consists of two distinct coats, and observed the spines and sculpturings on the outer coat and its elasticity; he observed the lids of the orifices in the exine of Passiflora coerulea, and went as far as to see the interior coat in moistened pollen-grains protrude in the form of conical projections, which then nonetheless burst and allowed the contents to flee.
He goes on to say that he grounds his idea of flowers on these his six chief discoveries made in the course of 5 years; he then gives his principle at length, first of all explaining the nature of juice-secreting glands (nectaries), and organs for receiving or protecting the nectar, and the contrivances for enabling insects to find their manner readily to the juice. Since Darwin breathed new life into these ideas by the idea of choice, Sprengel has been recognised as certainly one of its chief helps. The plant-collectors of the Linnaean school as well because the true systematists at the end of the 18th century had little understanding for such labours as Koelreuter’s, and incorrect ideas on hybrids and their energy of maintaining themselves prevailed despite them in botanical literature. Hybrids had been necessarily in- handy to the believers in the constancy of species; they. He exhibits at the same time from experiment, that if the stigma of a plant receives its own pollen and pollen from another plant at the identical time, the previous only is effectual, and that this is one motive why hybrids which might be raised artificially should not present in nature.
Then he exhibits how his principles explain all of the physiological characters of flowers, position, measurement, color, odor, form, time of flowering and the like. The mingling of the characters of the 2 mother and father was the very best refutation of the speculation of evolution, and equipped at the identical time profound views of the true nature of the sexual union. In his work, ‘Das neu entdeckte Geheimniss der Natur in Bau und Befruchtung der Blumen,’ Berlin, 1793, he says at web page 43: ‘Since very many flowers are dioecious, and doubtless at least as many hermaphrodite flowers are dichogamous, nature seems not to have intended that any flower ought to be fertilised by its own pollen.’ This was nonetheless only considered one of his shocking conclusions; still more essential perhaps was the view, that the construction and all of the peculiar characters of a flower can solely be understood from their relation to the insects that visit them and impact their pollination ; right here was the first attempt to clarify the origin of natural types from definite relations to their setting. Konrad Sprengel also fully dedicated himself to this view, and was thereby prevented from understanding the technique of fertilisation in Asclepiadeae. In an investigation which he made in 1775 into the circumstances of pollination in Asclepiadeae he reverted to this idea, and insisted that the act of fertilisation in the whole vegetable and animal kingdom is a mingling of two fluids.