A Manual of Botany
BEFORE investigating the nature of the process of germination, or "sprouting," it may be well to discuss a few points regarding the vitality of seeds—a subject which is of the greatest importance not only in physiological but in geographical botany.
1862-63, S. 77 (fide Johnson).
Duration of Vitality.—If seeds are kept dry, the embryo remains dormant; but the time during which the embryo will retain its vitality varies much with the seeds of different species. For instance, it is said that the seeds of willow will not grow after having been once dry, and that if even kept fresh they lose their germinating power in two weeks. The seeds of coffee and other Rubiaceae, Angelica, and other Umbelliferae, do not germinate freely after having been kept for any length of time. The seeds of wheat usually lose the power of growth after being kept seven years, though it has been found quite capable of being used as food even after being kept more than two centuries. The stories about "mummy wheat" sprouting after remaining in Egyptian tombs for thousands of years are, to say the least of them, very dubious, no well-authenticated instance of such being extant; while among other articles sold by the Arabs to credulous travellers, as coming out of the same tombs as this ancient wheat, have been dahlia bulbs and maize—the deposition of which in the receptacles from which they were said to be extracted necessitating the belief that 3000 years ago the subjects of the Pharaohs were engaged in commerce with America! Dietrich1 experimented with the seeds of wheat, rye, and a species of Bromus 185 years old, but failed to induce them to germinate, the place of the embryo being occupied by a slimy putrefying fluid.
|1Sur la durée de la faculté de Germiner, &c.; Ann. des Sc. Nat., 1846 (t. vi.), p. 373-382; Ann. Nat. Hist., 1st ser., XX. 38; Lefebure, Sur la Germination des Plantes, 1804; Gerardin, Sur la propriété des Graines de conserver Iongtemps leur vertu germinative, 1809; British Assoc. Rep., 1850, p. 62; &c.|
of Selborne (Blyth's ed.), p. 300.
2Macgillivray, Edin. Journ. of Nat. Hist. and Phys. Sc., 1836, p. 35.
3These and various similar facts are given at length in an anonymous little work published at Edinburgh in 1835, entitled the 'Physiology of Plants; or, the Phenomena and Laws of Vegetation,' which contains some original matter worthy of attention.
If, however, excluded from the air, damp, &c., seeds have been known to keep for somewhat lengthened periods. For instance, those of leguminous plants have been known to sprout after being kept dry for 60 years. In 1810, fruit was obtained in the Jardin des Plantes from a species of Phaseolus or Dolichos taken from the herbarium of Tournefort, who flourished about 1694. The seeds of the sensitive plant have germinated after being kept 60 years; while Gerardin records that haricot-beans, after being kept for more than too years in herbaria, sprouted. Rye has been said to have sprouted after 140 years (Home). Alphonse de Candolle found, from experiments in the Geneva Botanic Garden, that large seeds keep longer than small ones, and that the germinating power of seeds was in an inverse ratio to the rapidity of germination.1 The seeds of woody species seemed to preserve their vitality longest, and biennials shortest; while those of perennials were longer-lived than those of annuals. Seeds of the ordinary Rubus Idaeus, or raspberry, found in a British tumulus near Maiden Castle, Devonshire, in 1834, along with coins of the Emperor Hadrian (and therefore, if contemporaneous, sixteen or seventeen hundred years ago), germinated under the care of Professor Lindley, and produced vigorous fruiting plants. M. Charles Desmoulin also generated seeds of Medicago lupulina, Centaurea Cyanus, Heliotropium Europaeum, &c., found in Roman tombs dating most probably to the second or third century of our era. Numerous instances are recorded of seeds which have been supposed to be buried in the soil under old houses springing up; but most of these cases must be viewed with a certain degree of scepticism, the openings for error or deception being too many. As one specimen, I quote the following instance, communicated in 1866 to the Botanical Society of France, and said to be authentic: Under the foundations of a very ancient building demolished recently in the "Ile de la Seine" where the city was founded, Dr Boisduval took a quantity of blackish earth, in the midst of which an attentive examination revealed the presence of seeds. These seeds, grown with great care under a bell-glass, or "cloche," gave origin to plants of Juncus bufonius, L., a plant of moist places and grounds inundated during the winter—i.e., growing ordinarily in conditions similar to that presented by the ground on which was built the ancient city of Lutetia! Gilbert White long ago noted that, when beech-trees were cleared off from the "Hanger" at Selborne, the ground got covered with strawberry plants, which might have probably lain in the ground for many years, but could not vegetate till the sun and air were admitted; and that places, where in his day, and for a century before, beech-trees had grown, were known to the people by the name of strawberry "slides" or trenches, though no strawberries had grown there in the memory of man.1 In some experiments made in 1817 by Sir Thomas Dick Lauder, he found that four species of plants (Hieracium pilosella, Myosotis scorpioides, Lamium purpureum, and Spergula arvensis) germinated in soil taken from beneath a covering of sand, which had lain over a portion of Morayshire for at least sixty years.2 Numerous such cases could be quoted. For instance, maize from the tombs of the Incas of Peru—and therefore probably at least 300 years old—has been known to germinate. Seeds of ragwort taken from the centre of a solid mass of peat-earth, at a depth of 16 feet, in a bog in the Isle of Man, have germinated. Some hazelnuts, discovered at a considerable depth in a morass in the county of Durham, grew when sown, &c.3
Nat. Hist., 1st ser., xiii. 89.
5The vitality of seeds will be discussed at
greater length in PHYTO-GEOGRAPHY.
Kemp4 records an instance of having germinated seeds of Polygonum Convolvulus, Rumex Acetosella, and an Atriplex, taken from the depth of 25 feet in a sand-pit near Melrose, and in regard to which he had satisfied himself that there had been no deception or error. He considered that they might have been more than 2000 years old. Mr Grugeon has communicated to me a similar instance of vitality in buried seeds of a Rumex. It therefore appears that if seeds are buried at a depth in the soil where they may be removed from the influence of light, heat, oxygen, and other conditions of germination, they may preserve their vitality for a considerable period; but there are so many probabilities of mistake or collusion to be eliminated, that any extraordinary cases of vitality reported require to be carefully examined before anything like implicit credence is given to them. On the whole, it may be said that the rule is, that the fresher seeds are, the more certainty there is of their germinating, and that the percentage which spring is in a tolerably direct ratio to their age.5
Londet and Haberlandt made experiments with cereals which proved this decisively. The following table gives the results of the latter observer:—
|Name of grain||Percentage of seeds that germinated in 1861, from the years|
|1I am informed by my friend Mr Wm. Gorrie, of Trinity, Edinburgh, a very experienced scientific agriculturist, that the same fact has been noticed among agricultural plants. For instance, the late Mr Oliver, of Lochend, near Edinburgh, found that two-year-old turnip-seed produced larger bulbs and less leaf than fresher seed. The ordinary garden balsam also produces more flowers and less leaves if kept some time than if sown the first year.|
Results of the Use of long-kept Seeds.—Old seeds yield weak plants, and this peculiarity is taken advantage of by horticulturists in producing new varieties. It is said that while one-year-old seeds of the ten-week stock yielded single flowers, those which had been kept four years produced, for the most part, double flowers, which are a monstrosity, the result of feebleness in the constitution of the plant (p. 385). From observations made at the instance of the Prussian Horticultural Society by Schmidt, Sprengel, D'Arenstorff, Treviranus, and Voss, it has been found, as a general result, that in the case of melons and cucumbers, the longest-kept seeds, though less certain to germinate, yet yielded the greatest amount of fruit; while new seed produced vigorous plants, which ran too much to leaf.1 M. Voss reared, from 24 seeds of a Spanish melon thirty years old, eight plants which gave good fruit. Cucumber-seeds 17 years old gave the same result; while some seeds of Althaea rosea (hollyhock) 23 years old afforded well-conditioned plants. It was found, by most of the above observers, that plants obtained from the seeds of the preceding year produced many leaves but few fruitful flowers, and almost entirely male ones; but that these same seeds, dried by the heat of the sun or of a stove, yielded a greater number of fruitful plants, and that it is particularly at the end of some years they acquire this property. Erasmus Darwin accounts for the greater fruiting powers of old seeds by supposing that the cotyledons may receive some damage from keeping, which prevents their nourishing the young plant at its first germination so perfectly as they could otherwise have done.
sur la germination des Céréales, journal d'Agric. pratique, 1853, 3e sér. (t. vi.), p. 177-180
2Beiträge zur Phys. der Samens; flora, 1849; and Symbola at Seminis physiologiam, 1849 (Berlin), which I only know from quotation.
Treviranus argued stoutly that unripe seeds could not germinate—and certainly the common-sense prejudices of ordinary observers were with him. But this has been shown to be erroneous. Duhamel germinated green seeds of the oak; Senebier, green peas; Seiffert, haricot-beans, lentils, peas, broom, &c., which were not half grown; and the Styphnolobium of Japan, which cannot ripen its seeds in the Breslau Gardens, is nevertheless, according to Göppert, multiplied by incompletely-developed seeds. The only difference is, that these unripe seeds are a little longer in germinating than the ripe ones. Various observations have been made by Göppert, Duchartre,1 and others, with cereals and cultivated grasses, with a similar result. Again, we are told by Von Martius that the Brazilians always propagate Willughbeia speciosa by unripe seeds, considering that the fruit from plants thus obtained is better than that from trees grown from matured seed. It appears, therefore, that the faculty of germination does not depend upon the seed having attained its maturity, but dates to a period anterior to this. In plants belonging to many natural orders, the seed can germinate when it has advanced but a short way to maturity; but it is necessary that the embryo should have advanced some considerable way, and that the albumen has taken some degree of consistency. In general, Ferdinand Cohn found that plants reared from such seeds were not feebler than others.2
|3Lucanus, Versuch.-Stat., iv. s. 253.|
Unripe Seeds.—All authors are, however, agreed, that if seeds are gathered when unripe—even when the kernel is soft and milky, or even before the starch has formed and the kernel is like water in appearance—they are "capable of germination if allowed, after ripening, to dry in connection with the stem." Many, however, do not come up: and at first those which do germinate yield weak plants, and give a poor harvest in poor soil; but in rich soil the crop is as vigorous as that produced from ripe seed.3 The sowing of unripe peas produces earlier varieties. In the words of Liebig, "the gardener is aware that the flat and shining seeds in the pods of the stock gilly-flower will give late plants with single flowers, while the shrivelled seeds will furnish low plants with double flowers throughout"
Nat. Laws of Husbandry,
Engl. trans. (1813), p. 7.
Dwarfed or Light Seeds.—Light seeds sprout quicker, but yield weaker plants, and are, in addition, not so sure of germinating as heavy grains. The number of roots, and the strength of these roots formed in the process of germination, are (as regards their non-nitrogenous constituents) in direct proportion to the amount of starch in the seed.4 We must, however, remember that the vigour of plants is not altogether dependent on the causes we have sketched out in the preceding pages, but that allowance must be made for the depth of soil they are laid in, and the stores of nourishment the plant may find there when it first begins to lead an existence independent of the seed.
|1For full account, see the Cirencester Agricultural Essays, edited by the Rev. J. Constable, entitled Practice with Science, 1867, p. 107, 342, 345; and abstract in Johnson, op. cit., p. 295.|
Value of Seed as regards Density.—Church found, from his experiments at Cirencester, that the value of seed-wheat stands in a certain connection with its specific gravity, and that (1) the seed-wheat of the greatest density produces the densest seed; (2) that the densest seed produces the greatest amount of dressed corn; (3) seed-wheat of medium density generally gives the largest number of ears, but the ears are poorer than those of the densest seed; while, again, (4) seed-wheat of medium density generally produces the largest number of fruiting plants. Though I am not aware that these and other observations made by this eminent chemist have yet been repeated by any other observer, the care with which they were made precludes the likelihood of any error. 1