Sessiliflora, after fertilization, enlarged.
The study of the fertilization, or as it is now generally called "pollination," of flowers, was continued by Darwin and taken up by other workers, notably Friedrich Hildebrand, Federico Delpino and the brothers Fritz and Hermann Muller.
Only where there is no such struggle for existence does self-fertilization often prove satisfactory for many generations."
Cross fertilization, or the impregnation of any given flower by pollen from another flower of the same species on the same or on another plant, has been proved to be of great - g advantage to the plant by securing a more FIG.
The anthers are so situated that the pollen on escaping comes into contact with the stigma; in such flowers self-fertilization is compulsory and very effectual, as seeds in profusion are produced.
The whole subject of fertilization and development of the embryo has been more recently investigated with great assiduity and zeal, as regards both cryptogamous and phanerogamous plants, and details must be sought in the various special articles.
This is a necessary consequence of the fusion of two nuclei in fertilization, unless the chromosomes are to be doubled at each generation.
The closed ovary implies a mode of fertilization which is profoundly different, and which was probably correlated with a simultaneous development of insect life.
These illustrations are comparatively simple; it would have been easy to select others of a more complicated nature, but all evidently connected with the visits of insects and the cross fertilization of the flower.
In subsequent generations produced by self-fertilization of the hybrids it was found that the positive character was not present in all the individuals, but that a result was obtained showing that in the formation of the reproductive cells (ova and sperms) of the hybrid, half were endowed with the positive character and half with the negative.
Botanists were for a long time content to know that the scattering of the pollen from the anther, and its application to the stigma, were necessary for the production of perfect seed, but the stages of the process of fertilization remained unexplored.
Angulata) have the sexes separate, and fertilization is effected in the open water after the discharge of the ova and the spermatozoa from the females and males respectively.
In these cases we should expect to find some reduced process of fertilization similar to that of Humaria granulata among the ordinary Ascomycetes, where in the absence of the antheridia the female nuclei fuse in pairs.
This c and common cross fertilization is often effected by the gland g.
See Darwin's Fertilization of Orchids and similar works.
Fertilization is effected by insects, especially by bees, which are directed in their search by the colour and fragrance of the flowers; but some pollen must also be transported by the wind to the female flowers, especially in arctic species which, in spite of the poverty of insect life, set abundant fruit.
The greatest difference of opinion exists among botanists as to their number and the bounds to be assigned to each; and the cross-fertilization that takes place between the species intensifies the difficulty.
In 1799 an Englishman, Thomas Andrew Knight, after experiments on the cross-fertilization of cultivated plants, formulated the conclusion that no plant fertilizes itself through many generations.
There was thus very strong circumstantial evidence in favour of fertilization, although the male nucleus was not traced.
Culture of classical ages was slightly more developed in Greece so far as the husbandman of Greece and Rome was less able to leave to nature the fertilization of the soil.
Her oldest priestesses, the dew-sisters - Aglauros, Herse, Pandrosos - signify the fertilization of the earth by the dew, and were probably at one time identified with Athena, as surnames of whom both Aglauros and Pandrosos are found.
The irregular construction of the flower is connected with fertilization by insect agency.
The proboscis, passing down this groove to the spur, becomes dusted with pollen; as it is drawn back, it presses up the lip-like valve of the stigma so that no pollen can enter the stigmatic chamber; but as it enters the next flower it leaves some pollen on the upper surface of the valve, and thus cross-fertilization is effected.
The most important work in this direction has been done by Fritz Muller (Filr Darwin), by Herman Muller (Fertilization of Plants by Insects), Grade b.
Do not ripen their fruit owing to imperfect fertilization, - is to be sought in this natural tendency to dioecism.
Coincidently, to allow of fertilization and the escape of excess of yolk, and of spermatozoa, other accessory ducts open at this point.
In the endoparasitic trematodes the uterus is the only passage by which fertilization can be effected, and in cases of cross and selfimpregnation this duct is physiologically a vagina.
They differ structurally from the normal form in being capable of self-fertilization only, and in the shape and details of their spermatozoa.
Darwin's works on dimorphic flowers and the fertilization of orchids gave powerful support to this statement.
It should be noted that butterflies are the chief agents in securing the continued existence of such alpine flowers as depend on insect fertilization, the other insect fertilizers being mostly wanting at great heights.
After fertilization the female cell, now called the oospore, divides and part of it develops into the embryo (new sporophyte), which remains dormant for a time still protected by the ovule which has developed to become the seed.
