The Garden 49(1264): 91 (Feb 8, 1896)
THE GERMINATION OF UNRIPE SEEDS
F. W. Burbidge
A RECENT article in a contemporary on Mr. J. C. Arthur's paper (Gardeners' Chronicle, p. 110) is very suggestive, and ought to lead to some very interesting practical applications on the part of gardeners and amateurs. Of course, it has long been known that many seeds will germinate long before they are ripe enough to be kept or preserved in a dry condition. In a word, it is evident that from a gardener's point of view seeds are ripe enough to germinate and grow long before they are ripe enough for the seedsmen and the millers. The behaviour of grain crops, such as Wheat, after a cold and wet season is a case in point, much corn being lost by its growing in the ear, in some cases even before it is cut, but more frequently in the sheaves and the stocks, during prolonged wet harvest weather. The worse the grain is developed from a miller's point of view, the more readily it seems to grow, or, in other words, its power of growth seems to be in inverse proportion to its stowage or grinding qualities. In effect it is, as stated, a weakening of the link that binds one generation to another in the vegetable world, and, of course, we know that weakened plants are as a rule more precocious and very often more fertile than the strongest ones. I do not say that their offspring are as well fitted for a natural existence, or that they are as healthy and strong or as long-lived as those from well ripened seeds; all I say is that they are generally more precocious and often more numerous.
It is after all a mere question of nutrition, and, in connection with Melon seeds, I may say that it was, and is even still, a rule for gardeners to carry Cucumber, Melon, Tomato and other seeds in their waistcoat pockets for a week or two or even longer previous to sowing them. A still older plan was to keep the seeds in a dry cupboard or drawer for a year or two before they were sown, the result being in each case substantially the same, viz., a weakening of the seed, which caused earlier fertility—in other words, loss of energy in the seeds, caused a vegetative growth less rampant, and one result of this in the case of dioecious plants is a larger proportion of female flowers or a stronger development of the female portion of hermaphrodite blossoms, and, of course, a larger crop of fruits in numbers, though possibly not always larger in bulk or in weight.
All this is far from being as trivial as to some it may perchance appear, since, by altering the richness of the soil in which seedling plants are grown, we can in some cases prolong or accentuate the differences in cropping obtainable by sowing fully grown, but unripe seeds. By "unripe" I mean to convey the notion of seeds that are ripe enough to grow, but not ripe enough to dry and keep or preserve. One of the very earliest records I have met with having a bearing on the question as to the proportion of the sexes of dioecious seeds being varied according to varied nutrition is in Threlkeld's "Synopsis Stirpium Hibernicarum," published in Dublin in 1727. Under the heading of "Cannabis mas (male Hemp)," Threlkeld speaks as follows: "The male Hemp (female) has the seed, the female (male) only flowers, yet both are procreated from the same seed. The more attentive husbandmen observe that in a fat soil you have more of the male Hemp, in a lean soil more of the female, or, where it is sown too thick and so wants nutritious juice, it is female. This is a devouring plant and requires well-dunged ground, as Hops do." Threlkeld's inversion of the sexes was usual at the time when the largest plants were dubbed "males," and the smaller or more slender "female," of which our Male Fern and Lady Fern serve to-day as examples. Making this allowance, we perceive that the husbandmen had reached to a state of knowledge a century and a half ago that is even to-day not generally "understanded of the people." It is very probable that by applying the facts suggested, let us say, to the rearing of seedling Hops, a stronger, hardier, and more fertile race or strain could be obtained. In the animal kingdom similar results have been obtained by the feeding and starving of frog spawn, as mentioned in Geddes' and Thompson's "Evolution of Sex," a book of great interest, but one singularly weak in its vegetable biology as compared with its zoological information.
The practical point for cultivators is to note that they can within certain limits actually influence the progeny of dioecious and monoecious plants such as Melons, Cucumbers, Gourds, Hemp, Hops, Aucubas, Nepenthes, &c, so far as the proportions of male and female flowers, or male and female plants are concerned. There are various other ways, however, often available to gain or to facilitate the same end; for example, a starved plant yields more male flowers and a well-fed one more females, so that even the seed may have a vegetative, apart from a sexual, bias or tendency given to it while still connected with the mother plant. Again, we see that unripe seed tends to afford plants yielding an earlier crop than does well-ripened seed, but practically a similar result may sometimes be gained by sowing well-ripened seeds in a poor soil, taking care not to water the seedlings too freely; but, as previously remarked, all other factors being equal, unripe seed or seeds that have been kept dry a long time is the more precocious all the same.
In this connection we may consider how many of our field and garden crops, usually increased by vegetative methods rather than by seeds, rapidly deteriorate, even under the best and most varied of cultural conditions. The Potato, the Vine, the Sugar-cane, as well as the Hop plant are well-known examples. Nature not only abhors continual self-fertilisation, but she also hates, in only a slightly less degree, continual vegetative propagation from cuttings or grafts, &c. All cultivated life shows a tendency to degradation, and a wearing-out process is continually going on, and all our cultural methods with such crops—viz, change of soil and climate and abundance of suitable food—are merely palliative and no cure. Good culture retards the process of wearing out, but does not prevent it in the end. The real new life or renewal must be by seeds.
The genus Primrose is peculiarly liable to come very eratically and unequally from seeds that have been dried and stored after thorough ripening. On the other hand, seeds gathered long before the capsules or seed vessels burst open and sown at once germinate much earlier and abundantly, and the same is true of many other plants and flowers. After all, this is only what Nature shows us every day, by sowing her seeds as soon as they are ripe or as soon as the seed vessels open, which is often long before the seeds are ripe from a seedman's point of view.
Of course seed sowing is one of the most important factors in plant culture, and I have for many years been continually carrying out experiments in sowing seeds direct from the parent plants, that is, as soon as ever they reach the germination stage, as well as in the spring after they had become thoroughly ripe and had been kept in a dry cupboard all the winter. In the majority of cases I have been most successful with the newly-sown seeds. They germinate earlier and more equally, they afford plants that flower earlier, are dwarfer and more compact in habit, and are frequently more fertile, i.e., become better seed-bearers themselves from the gardener's point of view, which is, as I have said, nearly always more or less different from what may be called Nature's point of view. It will be most interesting to hear the experience of other cultivators who raise seedlings of garden plants, such as Rev. C. Wolley-Dod, Rev. G. H. Engleheart, Mr. R. Lindsay, Mr. R. Irwin Lynch, Mr. W. Watson, and many of our successful trade growers of florists' flowers could afford much valuable information. I have rarely read a more suggestive paper, and it is to be hoped that all who are interested in the development of new early flowering or fruiting strains of garden plants will utilise the hints thrown out for their guidance.
It is apparent that the continued sowing of rath-ripe seeds is conducive to precocity, and also to an enhanced crop of flowers and fruits in proportion to the vegetative area of the plant; in a word, the dynamic force of a plant is altered, so as to facilitate the production of one kind of growth or produce at the expense of another, and the best results will, of course, be gained by a rich feeding when leaf, root or stem crops are sought for, but in the case of flowers and fruits the method of culture must be one of judiciously withholding all surplus nutriment until after the desired results are evident and the initial budding or the actual fruit setting is fully assured, when a more liberal course of treatment may be adopted with safety and advantage.