In the pea itself we have every tint between almost pure white, brown, yellow, and intense green; in the varieties of the _Sugar peas_ we have these same tints, together with red passing through fine purple into a dark chocolate tint. These colours are either uniform or distributed in dots, striæ, or moss-like marks; they depend in some cases on the colour of the cotyledons seen through the skin, and in other cases on the outer coats of the pea itself. In the different varieties, the pods contain, according to Mr. Gordon, from eleven or twelve to only four or five peas. The largest peas are nearly twice as much in diameter as the smallest; and the latter are not always borne by the most dwarfed kinds. Peas differ much in shape, being smooth and spherical, smooth and oblong, nearly oval in the _Queen of the Dwarfs,_ and nearly cubical and crumpled in many of the larger kinds.
With respect to the value of the differences between the chief varieties, it cannot be doubted that, if one of the tall _Sugar-peas,_ with purple flowers, thin-skinned pods of an extraordinary shape, including large, dark-purple peas, grew wild by the side of the lowly _Queen of the Dwarfs,_ with white flowers, greyish-green, rounded leaves, scimitar-like pods, containing oblong, smooth, pale-coloured peas, which became mature at a different season: or by the side of one of the gigantic sorts, like the _Champion of England,_ with leaves of great size, pointed pods, and large, green, crumpled, almost cubical peas,—all three kinds would be ranked as distinct species.
Andrew Knight[85] has observed that the varieties of peas keep very true, because they are not crossed by insects. As far as the fact of keeping true is concerned, I hear from Mr. Masters of Canterbury, well known as the originator of several new kinds, that certain varieties have remained constant for a considerable time,—for instance, _Knight’s Blue Dwarf,_ which came out about the year 1820.[86] But the greater number of varieties have a singularly short existence: thus Loudon remarks[87] that “sorts which were highly approved in 1821, are now, in 1833, nowhere to be found;” and on comparing the lists of 1833 with those of 1855, I find that nearly all the varieties have changed. Mr.
Masters informs me that the nature of the soil causes some varieties to lose their character. As with other plants, certain varieties can be propagated truly, whilst others show a determined tendency to vary; thus two peas differing in shape, one round and the other wrinkled, were found by Mr. Masters within the same pod, but the plants raised from the wrinkled kind always evinced a strong tendency to produce round peas. Mr. Masters also raised from a plant of another variety four distinct sub-varieties, which bore blue and round, white and round, blue and wrinkled, and white and wrinkled peas; and although he sowed these four varieties separately during several successive years, each kind always reproduced all four kinds mixed together!
With respect to the varieties not naturally intercrossing, I have ascertained that the pea, which in this respect differs from some other Leguminosæ, is perfectly fertile without the aid of insects. Yet I have seen humble-bees whilst sucking the nectar depress the keel-petals, and become so thickly dusted with pollen, that it could hardly fail to be left on the stigma of the next flower which was visited. Nevertheless, distinct varieties growing closely together rarely cross; and I have reason to believe that this is due to their stigmas being prematurely fertilised in this country by pollen from the same flower. The horticulturists who raise seed-peas are thus enabled to plant distinct varieties close together without any bad consequences; and it is certain, as I have myself found, that true seed may be saved during at least several generations under these circumstances.[88] Mr. Fitch raised, as he informs me, one variety for twenty years, and it always came true, though grown close to other varieties. From the analogy of kidney-beans I should have expected[89] that varieties thus circumstanced would have occasionally crossed; and I shall give in the eleventh chapter two cases of this having occurred, as shown (in a manner hereafter to be explained) by the pollen of the one variety having acted directly on the seeds of the other. Whether many of the new varieties which incessantly appear are due to such occasional and accidental crosses, I do not know. Nor do I know whether the short existence of almost all the numerous varieties is the result of mere change of fashion, or of their having a weak constitution, from being the product of long-continued self-fertilisation. It may, however, be noticed that several of Andrew Knight’s varieties, which have endured longer than most kinds, were raised towards the close of the last century by artificial crosses; some of them, I believe, were still vigorous in 1860; but now, in 1865, a writer, speaking[90] of Knight’s four kinds of marrows, says, they have acquired a famous history, but their glory has departed.
With respect to Beans (_Faba vulgaris_), I will say but little. Dr.
Alefield has given[91] short diagnostic characters of forty varieties.
Everyone who has seen a collection must have been struck with the great difference in shape, thickness, proportional length and breadth, colour, and size which beans present. What a contrast between a Windsor and Horse-bean! As in the case of the pea, our existing varieties were preceded during the Bronze age in Switzerland[92] by a peculiar and now extinct variety producing very small beans.[93] _Potato (Solanum tuberosum)._—There is little doubt about the parentage of this plant; for the cultivated varieties differ extremely little in general appearance from the wild species, which can be recognised in its native land at the first glance.[94] The varieties cultivated in Britain are numerous; thus Lawson[95] gives a description of 175 kinds.
I planted eighteen kinds in adjoining rows; their stems and leaves differed but little, and in several cases there was as great a difference between the individuals of the same variety as between the different varieties. The flower varied in size, and in colour between white and purple, but in no other respect, except that in one kind the sepals were somewhat elongated. One strange variety has been described which always produces two sorts of flowers, the first double and sterile, the second single and fertile.[96] The fruit or berries also differ, but only in a slight degree.[97] The varieties are liable in very different degree to the attack of the Colorado potato-beetle.[98] The tubers, on the other hand, present a wonderful amount of diversity.
This fact accords with the principle that the valuable and selected parts of all cultivated productions present the greatest amount of modification. They differ much in size and shape, being globular, oval, flattened, kidney-like, or cylindrical. One variety from Peru is described[99] as being quite straight, and at least six inches in length, though no thicker than a man’s finger. The eyes or buds differ in form, position, and colour. The manner in which the tubers are arranged on the so-called roots or rhizomes is different; thus, in the _gurken-kartoffeln_ they form a pyramid with the apex downwards, and in another variety they bury themselves deep in the ground. The roots themselves run either near the surface or deep in the ground. The tubers also differ in smoothness and colour, being externally white, red, purple, or almost black, and internally white, yellow, or almost black. They differ in flavour and quality, being either waxy or mealy; in their period of maturity, and in their capacity for long preservation.
As with many other plants which have been long propagated by bulbs, tubers, cuttings, etc., by which means the same individual is exposed during a length of time to diversified conditions, seedling potatoes generally display innumerable slight differences. Several varieties, even when propagated by tubers, are far from constant, as will be seen in the chapter on Bud-variation. Dr. Anderson[100] procured seed from an Irish purple potato, which grew far from any other kind, so that it could not at least in this generation have been crossed, yet the many seedlings varied in almost every possible respect, so that “scarcely two plants were exactly alike.” Some of the plants which closely resembled each other above ground, produced extremely dissimilar tubers; and some tubers which externally could hardly be distinguished, differed widely in quality when cooked. Even in this case of extreme variability, the parent-stock had some influence on the progeny, for the greater number of the seedlings resembled in some degree the parent Irish potato. Kidney potatoes must be ranked amongst the most highly cultivated and artificial races; nevertheless their peculiarities can often be strictly propagated by seed. A great authority, Mr.
Rivers,[101] states that “seedlings from the ash-leaved kidney always bear a strong resemblance to their parent. Seedlings from the fluke-kidney are still more remarkable for their adherence to their parent stock, for, on closely observing a great number during two seasons, I have not been able to observe the least difference, either in earliness, productiveness, or in the size or shape of their tubers.”
REFERENCES [2] Review by Mr. Bentham in ‘Hort. Journal,’ vol. ix 1855, p. 133, entitled, ‘Historical Notes on cultivated Plants,’ by Dr. A.
une époque d’ignorance, plus il est probable que les cultivateurs avaient choisi des especes offrant à l’origine meme un avantage incontestable.”
[5] Dr. Hooker has given me this information. _See also_ his [6] ‘Travels in Central Africa,’ Eng. translat. vol. i. pp. 529 and [7] For instance in both North and South America. Mr. Edgeworth (‘Journal Proc. Linn. Soc.,’ vol. vi. Bot., 1862, p. 181) states that in the deserts of the Punjab poor women sweep up, “by a whisk into straw baskets,” the seeds of four genera of grasses, namely, of Agrostis, Panicum, Cenchrus, and Pennisetum, as well as the seeds of four other genera belonging to distinct families.
[8] Prof. O. Heer, ‘Die Pflanzen der Pfahlbauten, 1866, aus dem Neujahr. Naturforsch. Geselschaft,’ 1866; and Dr. H. Christ in 1861, p. 445.
[10] In Tierra del Fuego the spot where wigwams had formerly stood could be distinguished at a great distance by the bright green tint of the native vegetation.
[14] De Candolle has tabulated the facts in the most interesting [16] For Canada, _see_ J. Cartier’s Voyage in 1534; for Florida, _see_ Narvaez and Ferdinand de Soto’s Voyages. As I have consulted these and other old Voyages in more than one general collection of Voyages, I do not give precise references to the pages. _See also,_ for several references Asa Gray, in the ‘American Journal of Science,’ vol. xxiv.
Nov. 1857, p. 441. For the traditions of the natives of New Zealand 260.
[17] _See,_ for example, Mr. Hewett C. Watson’s remarks on our wild plums and cherries and crabs: ‘Cybele Britannica,’ vol. i. pp. 330, declares that he has found the types of all our cultivated varieties in wild seedlings, but then he looks on these seedlings as so many aboriginal stocks.
[19] Mr. Bentham, in his review, entitled ‘Hist. Notes on cultivated Plants,’ by Dr. A. Targioni-Tozzetti, in ‘Journal of Hort. Soc.,’ vol.
ix., 1855, p. 133. He informs me that he still retains the same opinion.
[20] ‘Géograph. Bot.,’ p. 928. The whole subject is discussed with admirable fulness and knowledge.
[21] Godron, ‘De l’Espèce,’ tom. ii. p. 72. A few years ago the excellent, though misinterpreted, observations of M. Fabre led many persons to believe that wheat was a modified descendant of Ægilops; but M. Godron (tom. i. p. 165) has shown by careful experiments that the first step in the series, viz. _ Ægilops triticoides,_ is a hybrid between wheat and _ Æ. ovata._ The frequency with which these hybrids spontaneously arise, and the gradual manner in which the _ Æ.
triticoides_ becomes converted into true wheat, alone leave any doubt with respect to M. Godron’s conclusions.
[23] Report to British Association for 1857, p. 207.
[26] Col. J. Le Couteur on the ‘Varieties of Wheat,’ pp. 23, 79.
[28] _See_ an excellent review in Hooker’s ‘Journ. of Botany,’ vol.
viii. p. 82 note.
[30] Ibid., tom. ii. p. 75.
[31] For Dalbret and Philippar, _see_ Loiseleur-Deslongchamps ‘Consid.
sur les Céréales,’ pp. 45, 70. Le Couteur on Wheat, pp. 6, 14-17.
[32] _See_ his Essay on ‘Pedigree in Wheat,’ 1862; also paper read before the British Association, 1869, and other publications.
Economy of Yorkshire,’ vol. ii. p. 9, remarks that “in every field of corn there is as much variety as in a herd of cattle.”
[37] Quoted by Godron, ‘De l’Espèce,’ vol. ii. p. 74. So it is, according to Metzger (‘Getreidearten,’ s. 18), with summer and winter barley.
p. 70. Many other accounts could be added.
[39] ‘Travels in North America,’ 1753-1761, Eng. translat., vol. iii p. 165.
[40] ‘Céréales,’ part ii. pp. 179-183.
‘Rural Econ. of Yorkshire,’ vol. ii. p. 9. With respect to similar cases of adaptation in the varieties of oats, _ see_ some interesting papers in the ‘Gardener’s Chron. and Agricult. Gazette,’ 1850, pp.
204, 219.
[42] ‘On the Varieties of Wheat,’ p. 59. Mr. Shirreff, and a higher authority cannot be given (‘Gard. Chron. and Agricult. Gazette,’ 1862, p. 963), says, “I have never seen grain which has either been improved or degenerated by cultivation, so as to convey the change to the succeeding crop.”
[46] Quoted by Le Couteur, p. 16.
[48] O. Heer ‘Die Pflanzen der Pfahlbauten,’ 1866. The following passage is quoted from Dr. Christ, in ‘Die Fauna der Pfahlbauten, von [49] Heer, as quoted by Carl Vogt, ‘Lectures on Man,’ Eng. translat., p. 355.
[50] _See_ Alph. De Candolle’s long discussion in his ‘Géograph.
[53] This maize is figured in Bonafous’ magnificent work, ‘Hist. Nat.
du Mais,’ 1836, Pl. v. bis, and in the ‘Journal of Hort. Soc.,’ vol.
i. 1846, p. 115, where an account is given of the result of sowing the seed. A young Guarany Indian, on seeing this kind of maize, told Auguste St. Hilaire (_see_ De Candolle, ‘Géograph. Bot.,’ p. 951) that it grew wild in the humid forests of his native land. Mr.
Teschemacher. in ‘Proc. Boston Soc. Hist.,’ Oct. 19th, 1842, gives an account of sowing the seed.
Metzger’s statements in accordance with those made by Bonafous in his great work ‘Hist. Nat. du Mais,’ 1836.
[56] Godron ‘De l’Espèce,’ tom. ii. p. 80; Al. De Candolle, ibid., p.
951.
[57] ‘Transact. Bot. Soc. of Edinburgh,’ vol. viii. p. 60.
[60] Ibid., p. 31.
iv. I have consulted an old English MS. translation.
cabbage-stalk is exhibited in the Museum at Kew.
from ‘Gartenflora,’ April, 1855.
[68] _See_ the elder De Candolle, in ‘Transact. of Hort. Soc.,’ vol.
v.; and Metzger ‘Kohlarten,’ etc.
[70] Alph. De Candolle, ‘Géograph. Bot.’ pp. 842 and 989.
22.
10.
more especially, ibid., 1868, p. 275: the writer asserts that he planted a variety of cabbage (_B. oleracea_) close to turnips (_B.
rapa_) and raised from the crossed seedlings true Swedish turnips.
These latter plants ought, therefore, to be classed with cabbages or turnips, and not under _B. napus._ [79] These experiments by Vilmorin have been quoted by many writers.
An eminent botanist, Prof. Decaisne, has lately expressed doubts on the subject from his own negative results, but these cannot be valued equally with positive results. On the other hand, M. Carrière has lately stated (‘Gard. Chronicle,’ 1865, p. 1154), that he took seed from a wild carrot, growing far from any cultivated land, and even in the first generation the roots of his seedlings differed in being spindle-shaped, longer, softer, and less fibrous than those of the wild plant. From these seedlings he raised several distinct varieties.
[81] Alph. De Candolle ‘Géograph. Bot.,’ 960. Mr. Bentham (‘Hort.
Journal,’ vol. ix. 1855, p. 141) believes that garden and field peas belong to the same species, and in this respect he differs from Dr.
Targioni.
[84] A variety called the Rounciva attains this height, as is stated by Mr. Gordon in ‘Transact. Hort. Soc.’ (2nd series), vol. i. 1835, p.
374, from which paper I have taken some facts.
[88] _See_ Dr. Anderson to the same effect in the ‘Bath Soc.
Agricultural Papers,’ vol. iv. p. 87.
[89] I have published full details of experiments on this subject in [93] Mr. Bentham informs me that in Poitou and the adjoining parts of France, varieties of _Phaseolus vulgaris_ are extremely numerous, and so different that they were described by Savi as distinct species. Mr.
Bentham believes that all are descended from an unknown eastern species. Although the varieties differ so greatly in stature and in their seeds, “there is a remarkable sameness in the neglected characters of foliage and flowers, and especially in the bracteoles, an insignificant character in the eyes even of botanists.”
[95] ‘Synopsis of the Vegetable Products of Scotland,’ quoted in [97] Putsche und Vertuch ‘Versuch einer Monographie der Kartoffeln,’ vol. iv. p. 325.
FRUITS. GRAPES: VARY IN ODD AND TRIFLING PARTICULARS—MULBERRY: THE ORANGE GROUP—SINGULAR RESULTS FROM CROSSING— PEACH AND NECTARINE: BUD VARIATION IN THEIR STONES— CHERRIES: SINGULAR VARIETIES OF—APPLE—PEAR—STRAWBERRY: INTERBLENDING OF THE ORIGINAL FORMS—GOOSEBERRY: STEADY INCREASE IN SIZE OF THE FRUIT—VARIETIES OF—WALNUT—NUT—CUCURBITACEOUS PLANTS: WONDERFUL VARIATION OF.
ORNAMENTAL TREES. THEIR VARIATION IN DEGREE AND FLOWERS. MULTIPLE ORIGIN OF MANY KINDS—VARIATION IN CONSTITUTIONAL PECULIARITIES—KIND OF VARIATION—ROSES: SEVERAL SPECIES CULTIVATED—PANSY—DAHLIA—HYACINTH: HISTORY AND VARIATION OF.
_The Vine (Vitis vinifera)._—The best authorities consider all our grapes as the descendants of one species which now grows wild in western Asia, which grew wild during the Bronze age in Italy,[1] and which has recently been found fossil in a tufaceous deposit in the south of France.[2] Some authors, however, entertain much doubt about the single parentage of our cultivated varieties, owing to the number of semi-wild forms found in Southern Europe, especially as described by Clemente[3] in a forest in Spain; but as the grape sows itself freely in Southern Europe, and as several of the chief kinds transmit their characters by seed,[4] whilst others are extremely variable, the existence of many different escaped forms could hardly fail to occur in countries where this plant has been cultivated from the remotest antiquity. That the vine varies much when propagated by seed, we may infer from the largely increased number of varieties since the earlier historical records. New hot-house varieties are produced almost every year; for instance,[5] a golden-coloured variety has been recently raised in England from a black grape without the aid of a cross. Van Mons[6] reared a multitude of varieties from the seed of one vine, which was completely separated from all others, so that there could not, at least in this generation, have been any crossing, and the seedlings presented “les analogues de toutes les sortes,” and differed in almost every possible character both in the fruits and foliage.
The cultivated varieties are extremely numerous; Count Odart says that he will not deny that there may exist throughout the world 700 or 800, perhaps even 1000 varieties, but not a third of these have any value.
In the catalogue of fruit cultivated in the Horticultural Gardens of London, published in 1842, 99 varieties are enumerated. Wherever the grape is grown many varieties occur: Pallas describes 24 in the Crimea, and Burnes mentions 10 in Cabool. The classification of the varieties has much perplexed writers, and Count Odart is reduced to a geographical system; but I will not enter on this subject, nor on the many and great differences between the varieties. I will merely specify a few curious and trifling peculiarities, all taken from Odart’s highly esteemed work[7] for the sake of showing the diversified variability of this plant. Simon has classed grapes into two main divisions, those with downy leaves, and those with smooth leaves, but he admits that in one variety, namely the Rebazo, the leaves are either smooth, or downy; and Odart (p. 70) states that some varieties have the nerves alone, and other varieties their young leaves, downy, whilst the old ones are smooth. The Pedro-Ximenes grape (Odart, p. 397) presents a peculiarity by which it can be at once recognised amongst a host of other varieties, namely, that when the fruit is nearly ripe the nerves of the leaves or even the whole surface becomes yellow. The Barbera d’Asti is well marked by several characters (p. 426), amongst others, “by some of the leaves, and it is always the lowest on the branches, suddenly becoming of a dark red colour.” Several authors in classifying grapes have founded their main divisions on the berries being either round or oblong; and Odart admits the value of this character; yet there is one variety, the Maccabeo (p. 71), which often produces small round, and large oblong, berries in the same bunch. Certain grapes called Nebbiolo (p. 429) present a constant character, sufficient for their recognition, namely, “the slight adherence of that part of the pulp which surrounds the seeds to the rest of the berry, when cut through transversely.” A Rhenish variety is mentioned (p. 228) which likes a dry soil; the fruit ripens well, but at the moment of maturity, if much rain falls, the berries are apt to rot; on the other hand, the fruit of a Swiss variety (p. 243) is valued for well sustaining prolonged humidity. This latter variety sprouts late in the spring, yet matures its fruit early; other varieties (page 362) have the fault of being too much excited by the April sun, and in consequence suffer from frost. A Styrian variety (p. 254) has brittle foot-stalks, so that the clusters of fruit are often blown off; this variety is said to be particularly attractive to wasps and bees. Other varieties have tough stalks, which resist the wind. Many other variable characters could be given, but the foregoing facts are sufficient to show in how many small structural and constitutional details the vine varies. During the vine disease in France certain old groups of varieties[8] have suffered far more from mildew than others. Thus “the group of Chasselas, so rich in varieties, did not afford a single fortunate exception;” certain other groups suffered much less; the true old Burgundy, for instance, was comparatively free from disease, and the Carminat likewise resisted the attack. The American vines, which belong to a distinct species, entirely escaped the disease in France; and we thus see that those European varieties which best resist the disease must have acquired in a slight degree the same constitutional peculiarities as the American species.
_White Mulberry (Morus alba)._—I mention this plant because it has varied in certain characters, namely, in the texture and quality of the leaves, fitting them to serve as food for the domesticated silkworm, in a manner not observed with other plants; but this has arisen simply from such variations in the mulberry having been attended to, selected, and rendered more or less constant. M. de Quatrefages[9] briefly describes six kinds cultivated in one valley in France: of these the _ amourouso_ produces excellent leaves, but is rapidly being abandoned because it produces much fruit mingled with the leaves: the _antofino_ yields deeply cut leaves of the finest quality, but not in great quantity: the _claro_ is much sought for because the leaves can be easily collected: lastly, the _roso_ bears strong hardy leaves, produced in large quantity, but with the one inconvenience, that they are best adapted for the worms after their fourth moult. MM.
Jacquemet-Bonnefont, of Lyon, however, remark in their catalogue (1862) that two sub-varieties have been confounded under the name of the roso, one having leaves too thick for the caterpillars, the other being valuable because the leaves can easily be gathered from the branches without the bark being torn.
In India the mulberry has also given rise to many varieties. The Indian form is thought by many botanists to be a distinct species; but as Royle remarks,[10] “so many varieties have been produced by cultivation that it is difficult to ascertain whether they all belong to one species;” they are, as he adds, nearly as numerous as those of the silkworm.
_The Orange Group._—We here meet with great confusion in the specific distinction and parentage of the several kinds. Gallesio,[11] who almost devoted his life-time to the subject, considers that there are four species, namely, sweet and bitter oranges, lemons, and citrons, each of which has given rise to whole groups of varieties, monsters, and supposed hybrids. One high authority[12] believes that these four reputed species are all varieties of the wild _Citrus medica,_ but that the shaddock (_Citrus decumana_), which is not known in a wild state, is a distinct species; though its distinctness is doubted by another writer “of great authority on such matters,” namely, Dr. Buchanan Hamilton. Alph. De Candolle,[13] on the other hand—and there cannot be a more capable judge—advances what he considers sufficient evidence of the orange (he doubts whether the bitter and sweet kinds are specifically distinct), the lemon, and citron, having been found wild, and consequently that they are distinct. He mentions two other forms cultivated in Japan and Java, which he ranks undoubted species; he speaks rather more doubtfully about the shaddock, which varies much, and has not been found wild; and finally he considers some forms, such as Adam’s apple and the bergamotte, as probably hybrids.
I have briefly abstracted these opinions for the sake of showing those who have never attended to such subjects, how perplexing they are. It would, therefore, be useless for my purpose to give a sketch of the conspicuous differences between the several forms. Besides the ever-recurrent difficulty of determining whether forms found wild are truly aboriginal or are escaped seedlings, many of the forms, which must be ranked as varieties, transmit their characters almost perfectly by seed. Sweet and bitter oranges differ in no important respect except in the flavour of their fruit, but Gallesio[14] is most emphatic that both kinds can be propagated by seed with absolute certainty.
Consequently, in accordance with his simple rule, he classes them as distinct species; as he does sweet and bitter almonds, the peach and nectarine, etc. He admits, however, that the soft-shelled pine-tree produces not only soft-shelled but some hard-shelled seedlings, so that a little greater force in the power of inheritance would, according to this rule, raise a soft-shelled pine-tree into the dignity of an aboriginally created species. The positive assertion made by Macfayden[15] that the pips of sweet oranges produced in Jamaica, according to the nature of the soil in which they are sown, either sweet or bitter oranges, is probably an error; for M. Alph. De Candolle informs me that since the publication of his great work he has received accounts from Guiana, the Antilles, and Mauritius, that in these countries sweet oranges faithfully transmit their character. Gallesio found that the willow-leafed and the Little China oranges reproduced their proper leaves and fruit; but the seedlings were not quite equal in merit to their parents. The red-fleshed orange, on the other hand, fails to reproduce itself. Gallesio also observed that the seeds of several other singular varieties all reproduced trees having a peculiar physiognomy, partly resembling their parent-forms. I can adduce another case: the myrtle leaved orange is ranked by all authors as a variety, but is very distinct in general aspect: in my father’s greenhouse, during many years, it rarely yielded any fruit, but at last produced one; and a tree thus raised was identical with the parent-form.
Another and more serious difficulty in determining the rank of the several forms is that, according to Gallesio,[16] they largely intercross without artificial aid; thus he positively states that seeds taken from lemon-trees (_C. lemonum_) growing mingled with the citron (_C. medica_), which is generally considered as a distinct species, produced a graduated series of varieties between these two forms.
Again, an Adam’s apple was produced from the seed of a sweet orange, which grew close to lemons and citrons. But such facts hardly aid us in determining whether to rank these forms as species or varieties; for it is now known that undoubted species of Verbascum, Cistus, Primula, Salix, etc., frequently cross in a state of nature. If indeed it were proved that plants of the orange tribe raised from these crosses were even partially sterile, it would be a strong argument in favour of their rank as species. Gallesio asserts that this is the case; but he does not distinguish between sterility from hybridism and from the effects of culture; and he almost destroys the force of this statement by another[17] namely, that when he impregnated the flowers of the common orange with the pollen taken from undoubted _varieties_ of the orange, monstrous fruits were produced, which included “little pulp, and had no seeds, or imperfect seeds.”
In this tribe of plants we meet with instances of two highly remarkable facts in vegetable physiology: Gallesio[18] impregnated an orange with pollen from a lemon, and the fruit borne on the mother tree had a raised stripe of peel like that of a lemon both in colour and taste, but the pulp was like that of an orange and included only imperfect seeds. The possibility of pollen from one variety or species directly affecting the fruit produced by another variety of species, is a subject which I shall fully discuss in the following chapter.
The second remarkable fact is, that two supposed hybrids[19] (for their hybrid nature was not ascertained), between an orange and either a lemon or citron, produced on the same tree leaves, flowers, and fruit of both pure parent-forms, as well as of a mixed or crossed nature. A bud taken from any one of the branches and grafted on another tree