This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
The ordinary monthly meeting of this Association was held in the Templar Hall, Reform Street, on Friday evening, the 5th ult. - the President, Mr Doig, Rossie Priory Gardens, in the chair. Mr James Grieve, Pilrig Park Nurseries, Edinburgh, read a paper on "Florists' Flowers." As subjects for his remarks he made choice of the Carnation, Pink, Phlox, Pentstemon, and the Viola and Pansy. These he considered the most valuable of the many so-called florists' flowers. He gave the first place to the Pinks and Carnations, than which no richer flowers were in cultivation. The herbaceous Phlox and the Pentstemon then claimed Mr Grieve's attention. Most of the florists' species of these, he said, were natives of America, and appear to have been introduced into this country at various times from 1732 to 1818. The Viola and Pansy were then treated of: though last on his list, they were by no means the least worthy. No other class of plants ranked higher in favour with the multitude; nor was this to be wondered at, seeing they flourished in almost any soil, blooming profusely in many cases from early spring to early winter. This was especially true of some of the bedding Violas introduced of late years, some of which might well be termed perpetual bloomers.
In treating these subjects, Mr Grieve detailed in full the most successful and approved methods of cultivation. In speaking of the culture of the Viola and Pansy, Mr Grieve (an acknowledged authority) said they were in many cases killed with over-kindness. All the knowledge required for even a novice might be contained in a nutshell. The first essential was deep digging, with a good supply of well-rotted manure; of equal importance, though less generally practised, was early planting and ptanting deep, at least up to within an inch of the head of the plant. Planted in this way, every eye under the surface would send up a shoot, and thus form fine bushy plants, while at the same time the roots would be protected from the summer drought. Another advantage gained by this system of planting was that it obviated the necessity of watering, which in the case of Pansies almost invariably produced scalding or damping off at the necks.
Mr John Nicoll, Arbroath, then read a most interesting and highly instructive paper on "Natural and Artificial Hybridisation." He introduced his subject by noticing the minute and intricate nature of the processes by which the reproduction of plants are effected, and proceeded to give a description of the various parts of a flower, pointing out those more immediately connected with the production of seed, - some of the most common modes by which fertilisation is effected being by agencies in some instances within, in others beyond, the flower. The wind and insects are the principal agents in this operation when the flower is not adapted for self-fertilisation, and observation shows how perfect are the means for accomplishing this object. When there is no gaily coloured flowers to allure insects, the pollen is light and powdery, and wind is commonly the means of transfer; but when flowers have bright-coloured corollas, there is also, in most cases, honey to induce the visits of insects, or at any rate pollen as food for the young of the domestic bee, and the pollen is of a gummy nature. Insects in quest of food carry off some of the pollen-grains, and in their visits to other flowers deposit at least a part of these grains on the stigma.
In addition to that class of plants which are unable to fertilise themselves in consequence of the sexual organs being on different plants, or at least in different flowers, there are others in which the sexual organs, though together, are not matured or sufficiently developed at the same time. Sometimes the stigma is in a ripe or receptive state long before the stamens are fully developed; while in other cases, the anthers shed the pollen-grains before the stigma is in a state to receive them. An example of this latter arrangement is to be seen in the Campanula family, where the pollen is not only shed, but in some cases the anthers are completely withered away before the stigma is fully developed. On the other hand, the Plantain or Ribgrass furnishes an example where the stigma has become developed and decayed before the stamens make their appearance on the same flower. The examples referred to will indicate that nature has made ample provision for cross-fertilisation, and that in the vegetable as well as in the animal world close breeding is provided against.
Mr Nicoll then spoke of the amazing number of the pollen-grains, and their great variety of form in different species. When pollen from the same flower, or different flowers on the same plant, or even from a different plant of the same species, is deposited on the stigma, and fertilisation follows, no change need be looked for in the future progeny from seed thus fertilised, further than may be produced by cultivation, change of soil, climate, or other extraneous conditions - in short, no hybrid form will result. It was only in cases of cross-fertilisation between two distinct species that a new form might be looked for. But even though no improvement, or even alteration, were to result, cross-fertilisation might be of great value in regard to the extra production of seed.
A Mr Williams, experimenting on the Victoria Regina, got the following results : a flower naturally fertilised produced 25 seeds; artificially fertilised with its own pollen, 60 seeds; artificially fertilised with pollen from a separate flower on the same plant, 100 seeds; while a flower fertilised with pollen from a separate plant produced 300 seeds, or 12 times that of the naturally fertilised flower. This showed how important, from a mercantile point of view, cross-fertilisation may become, if seeds entering largely in common use can be thus increased. In some parts of Germany, when fields of grain are in bloom, and the anthers in the act of shedding the pollen, a rope is drawn across the heads of the grain to insure better fertilisation than would be effected naturally. There had been considerable discussions as to whether the male or female elements have most influence in determining the character of the plant resulting from cross-fertilisation. Some have held the theory that the male parent has in all cases the greatest power; others hold that the result depends not upon the male parent, but upon the proportionate health and vigour of both parents.
It was reasonable to suppose that, if the male and female parents are equal in all respects, the progeny will show some intermediate characteristics; whereas, if one parent be superior in constitutional energy and sexual vitality, the future progeny may be expected to partake most of its distinctive features.
In closing his paper, Mr Nicoll pointed to the many inducements cross-fertilisation offered to the scientist, as well as to those who, caring little for the exactness of science, seek rather to increase the productions of nature, either for utility or beauty.