Naturalization (botany)

“ For this reason American gardeners will have to propagate their own plants and we shall have to use more native plants than European and Asiatic species, which made up the bulk of our gardening material in the past.
There are excellent reasons for using native shrubs upon quite other grounds than the difficulty or danger of importing foreign ones. Native plants fit into the natural landscape better than introduced sorts, and very often the garden enthusiast can go out into the country and dig out small specimens instead of buying them. ”

“ Therefore, when a cultivated species is found wild, frequently in Europe, more rarely in the United States, it is probable that, in spite of its indigenous appearance in America, it has become naturalized after being accidentally transported thither. ”

“ It is customary to speak of the British flora as consisting for the most part of species introduced into this country by natural means, while some plants owe their introduction to human agency or are 'escapes' from cultivation. It is by no means an easy task in some instances to decide whether a species is native or introduced, but in some cases, a few of which are mentioned, there is no doubt as to the alien nature of the plants. ”

“ Naturalizations produced in this manner often confound the wild plants with the cultivated ones, and the more easily that they fertilize each other since they belong to the same species. This fact is clearly demonstrated in the case of a plant of the old world cultivated in America, in gardens, and which, later, becomes naturalized on a large scale in the open country or the woods, like the cardoon at Buenos Ayres, and the oranges in several American countries. Cultivation widens areas, and supplements the deficits which the natural reproduction of the species may present. ”

“ I have referred to American fruit-trees, because we are not in this case troubled with doubts whether or not the varieties are seedlings which have escaped from cultivation. Transplanting any superior variety, or sowing its seeds, hardly implies more forethought than might be expected at an early and rude period of civilisation. Even the Australian barbarians "have a law that no plant bearing seeds is to be dug up after it has flowered;" ”

“ The law of analogous variation holds good with varieties produced by buds, as with those produced from seed: more than one kind of rose has sported into a moss-rose; more than one kind of camellia has assumed an hexagonal form; and at least seven or eight varieties of the peach have produced nectarines.
The laws of inheritance seem to be nearly the same with seminal and bud-varieties. We know how commonly reversion comes into play with both, and it may affect the whole, or only segments, of a leaf, flower, or fruit. ”

“ The balance of the reddish-purple plants, which comprise about two-thirds of the second generation, will, if their seeds are germinated, produce colored as against white-flowered progeny in the three-to-one ratio. In other words, these artificial crosses, made by the plant breeder, and this splitting up of hybrids which has been many times verified, are seen to be very fertile causes of the origin of new forms of plant life, if only the factor and character differences in the ancestry be sufficiently complex. ”

“ If the plant fertilizes itself without the aid of insects, as do some evening-primroses, the seed saved from the native locality may prove wholly pure, and if it does give rise to a uniform progeny the constancy of the race may be assumed to be proved, provided that repeated trials do not bring to light any exceptions. If the offspring shows more than one type, cross-fertilization is always to be looked to as the most probable cause, and should be excluded, in order to sow pure seeds. ”

“ Those which yielded a good crop for the first year have generally been found to produce seed, which, owing to the greater susceptibility of the plants to the attacks of insects, refused to germinate in the following year. Some of the lint produced was, apparently, of excellent quality and sold well, but the necessity for the renewal of seed each year formed a serious obstacle to the establishment of a new variety. The plants from American seed are not so hardy as those from native seed, and the necessity for greater care in cultivation renders them unsuitable for use by the natives. ”

“ A study of this species, as well as of plant-life in general, teaches us that nature abhors self-fertilization and, as a rule, so develops plants that two individuals of the same species are essential to the production of seed.
This species especially enjoys nature, and is not easily cultivated. A few florists have succeeded in producing mature plants with fair results, but it may be stated that even transplanting, with much soil attached to the roots, to a soil identical with the native, results in a weakened development. ”

“ In this way the nectar-seeking insects would often carry pollen from the flower of one plant to the stigma of another plant’s flower, and thus secure cross-fertilization. Undoubtedly often the stigma of a plant’s flower was fertilized by pollen from the same flower; but it is known that seeds produced by cross-fertilization are much more vigorous and hardy than those produced by self-fertilization in the same flower; therefore, those plants that varied most in the direction best adapted for securing cross-fertilization would have decided advantages in the struggle for existence. ”

“ Some of these endemic and naturalised plants are probably rendered sterile from excessive multiplication by buds, and their consequent incapacity to produce and nourish seed. But the sterility of others more probably depends on the peculiar conditions under which they live, as in the case of the ivy in the northern parts of Europe, and of the trees in the swamps of the United States; yet these plants must be in some respects eminently well adapted for the stations which they occupy, for they hold their places against a host of competitors. ”

“ No, the new Code deals, not with wild species, varieties and hybrids, but with what are commonly called "garden varieties"—namely, forms which have been brought into existence by selection, hybridization, or other similar processes devised by man, and are maintained in cultivation as clones or pure lines by man's care and skill—such plants as Rose 'Peace,' Apple 'Beauty of Bath,' and thousands of others. ”

“ When in bloom, the inferior sorts should be weeded out, retaining only the best varieties. To obtain seed true of any species, it is absolutely necessary to plant the separate kinds far apart, and cover them with fine muslin, to prevent the access of insects to the flowers, as none are more easily cross-fertilised. Division of the root is the only way to perpetuate any particular variety with certainty, unless seed is saved in the way mentioned, or imported from the native habitats of particular species. There are many beautiful hybrids, as well as species, in cultivation. ”

“ The same principle is seen in the naturalisation of plants through man's agency in foreign lands. It might have been expected that the plants which would succeed in becoming naturalised in any land would generally have been closely allied to the indigenes; for these are commonly looked at as specially created and adapted for their own country. It might also, perhaps, have been expected that naturalised plants would have belonged to a few groups more especially adapted to certain stations in their new homes. ”

“ In the case of varieties of the same species, the struggle will generally be almost equally severe, and we sometimes see the contest soon decided: for instance, if several varieties of wheat be sown together, and the mixed seed be resown, some of the varieties which best suit the soil or climate, or are naturally the most fertile, will beat the others and so yield more seed, and will consequently in a few years supplant the other varieties. ”

“ It is calculated that each jewel-weed blossom produces about two hundred and fifty pollen grains; yet each is by no means able to produce seed in spite of its prodigality. Nevertheless, enough cross-fertilized seed is set to save the species from the degeneracy that follows close inbreeding among plants as well as animals. In England, where this jewel-weed is rapidly becoming naturalized, Darwin recorded there are twenty plants producing cleistogamous flowers to one having showy blossoms which, even when produced, seldom set seed. ”

“ Within recent times, as far as animals are concerned, the crossing of distinct species has done little or nothing towards the formation or modification of our races. It is not yet known whether the several species of silk-moth which have been recently crossed in France will yield permanent races. With plants which can be multiplied by buds and cuttings, hybridisation has done wonders, as with many kinds of Roses, Rhododendrons, Pelargoniums, Calceolarias, and Petunias. Nearly all these plants can be propagated by seed, most of them freely; but extremely few or none come true by seed. ”

“ It must be added, however, that in the north of Europe and in the British Isles an extensive cultivation must have extended and multiplied naturalizations in comparatively modern times which can scarcely be now distinguished. ”

“ Do you not consider so many more seeds and plants being taken from Europe to America, than in a reverse direction, would go some way to account for comparative fewness of naturalised American plants here? Though I think one might wildly speculate on European weeds having become well fitted for cultivated land, during thousands of years of culture, whereas cultivated land would be a new home for native American weeds, and they would not consequently be able to beat their European rivals when put in contest with them on cultivated land. ”

“ 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, &c. ”

“ Cultivators speak of this or that kind as being remarkably constant or true; but by this they do not mean, as in other cases, that the kind transmits its character by seed, but that the individual plant does not change much under culture. The principle of inheritance, however, does hold good to a certain extent even with the fleeting varieties of the Heartease, for to gain good sorts it is indispensable to sow the seed of good sorts. ”

“ For fields where the colonies are small and scattered, this method of hoeing and shallow cultivation is probably the most practicable, as it helps to secure the early germination of any seeds that were left in the ground, and also kills them as soon as they are germinated. If the seed has developed, one must be careful not to spade it in too deep, as it may retain its vitality for some years if left covered in the moist soil. ”

“ Man takes plants westward, though a few migrate eastward.—So far as man's agency is concerned, the direction for plant migration is generally westward, in the course taken by himself. In case of two hundred kinds of weeds named by the United States Department of Agriculture, one hundred and eight species are of foreign origin. Three notable samples of weeds in the United States have gone from the west to the east, carried in seeds of grasses or clovers. ”

“ Other kinds were soon originated from seed by experimenters, and chance seedlings were found coming up in all fruit-growing regions. It was not long until there were hundreds of named varieties of good quality and that bore abundantly. Within the last decade or two there have been hundreds more originated by the most skillful hybridizers using our native species and the foreign ones also. Others just as good were picked up wherever they chanced to grow from seed. ”

“ Now, a cultivated plant which does not possess seeds must have been under culture for a very long period—we have not in Europe a single exclusively seedless, berry-bearing, cultivated plant—and hence it is perhaps fair to infer that these plants were cultivated as early as the beginning of the middle of the diluvial period. Moreover, the hypothesis of an immigration of the Indians via a still tropical Northern Asia and North America is confirmed by their going naked. ”

“ Now, what is the secret of the large, white daisy's triumphal conquest of our territory? A naturalized immigrant from Europe and Asia, how could it so quickly take possession? In the over-cultivated Old World no weed can have half the chance for unrestricted colonizing that it has in our vast unoccupied area. Most of our weeds are naturalized foreigners, not natives. ”

“ In horticultural practice a plant is not regarded as acquiring varietal status until it becomes distinctive among seedlings, because of superiority of product, unusual history, or other similar reason. Few tree varieties are recognized as such until after having been propagated by at least one asexual method, such as budding, grafting, layering or dividing. ”

“ Whenever it is profitable to a species to produce a large number of seeds and this obviously is a very common case, heterostyled will have an advantage over dioecious plants, as all the individuals of the former, whilst only half of the latter, that is the females, yield seeds. On the other hand, heterostyled plants seem to have no advantage, as far as cross-fertilisation is concerned, over those which are sterile with their own pollen. ”