| 单词 | self-fertilisation |
| 例句 | Rimpau confirms Darwin, H. Müller, and Ogle as to the self-fertilisation of our cultivated peas. Disease in Plants 2012-03-01T03:00:22Z My father had raised two beds of Linaria vulgaris—one set being the offspring of cross and the other of self-fertilisation. Charles Darwin: His Life in an Autobiographical Chapter, and in a Selected Series of His Published Letters 2012-01-22T03:00:19.733Z In cross-breeding, the conditions cease not only to be those of self-fertilising, but they cease, moreover, to be those of the close inbreeding of self-fertilisation. Feminism and Sex-Extinction 2011-11-11T03:00:29.100Z In the words of his own emphatic summing up, 'Nature abhors perpetual self-fertilisation.' Charles Darwin 2010-12-24T03:00:33.847Z Since none of them produce anything but whites on self-fertilisation it was found necessary to test their properties in another way, and the method adopted was that of crossing them together. Mendelism Third Edition Finally he concludes: “It is hardly an exaggeration to say that nature tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation”; and thus was announced a new doctrine in botany. Life of Charles Darwin Vegetable Kingdom, cross- and self-fertilisation in the, 47. Charles Darwin: His Life in an Autobiographical Chapter, and in a Selected Series of His Published Letters 2012-01-22T03:00:19.733Z In many other cases, far from there being any aids for self-fertilisation, there are special contrivances, as I could show from the writings of C. C. On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life. (2nd edition) In the more simple class self-fertilisation occurs freely, but it is prevented in the more complex flowers by the stamens maturing before the pistil. Darwinism (1889) Some of the kinds have their floral organs so arranged as to be capable of self-fertilisation; still, it is always as well to give them some assistance. Cactus Culture for Amateurs Being Descriptions of the Various Cactuses Grown in This Country, With Full and Practical Instructions for Their Successful Cultivation Mr. Kitchener has ingeniously explained the use of these movements, namely, to prevent the self-fertilisation of the flower. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Minute insects, such as Thrips, which sometimes haunt the flowers, would likewise be apt to cause the self-fertilisation of both forms. The Different Forms of Flowers on Plants of the Same Species Ophrys apifera, self-fertilisation of. -formation of pollen by a petal in. The Variation of Animals and Plants under Domestication — Volume 2 There are many plants, however, in which special arrangements exist to secure self-fertilisation. Darwinism (1889) All facts point clearly to eternal self-fertilisation in this species; yet I cannot swallow the bitter pill. More Letters of Charles Darwin — Volume 2 Notwithstanding that the self-fertilised plants in the second trial were the product of two additional generations of self-fertilisation, I cannot understand this discordance in the results of the two analogous experiments. Effects of Cross and Self Fertilisation in the Vegetable Kingdom In the case of Cephalanthera grandiflora I have shown that precocious and partial self-fertilisation, with subsequent full fertilisation, is the regular course of events. The Different Forms of Flowers on Plants of the Same Species I fancy that I see my way with the aid of continued self-fertilisation. More Letters of Charles Darwin — Volume 1 Yet in many of its close allies insect agency is absolutely required; but in one of these, the fly-orchis, comparatively very little seed is produced, and self-fertilisation would therefore be advantageous to it. Darwinism (1889) Darwin's interest in the Goodeniaceae was due to the mechanism being apparently fitted for self-fertilisation. More Letters of Charles Darwin — Volume 2 There is, however, but little danger of self-fertilisation until the bifid stigma opens; for Hildebrand found that pollen placed on the stigma before it had opened produced no effect. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Other species bear much less conspicuous flowers which secrete little or no nectar, and consequently are rarely visited by insects; these are adapted for self-fertilisation, though still capable of cross-fertilisation. The Different Forms of Flowers on Plants of the Same Species Any one who saw stamen after stamen bending upwards and shedding pollen over the stigmas of the same flower would declare that the structure was an admirable contrivance for self-fertilisation. More Letters of Charles Darwin — Volume 1 My father had raised two beds of Linaria vulgaris—one set being the offspring of cross- and the other of self-fertilisation. Life and Letters of Charles Darwin — Volume 2 I never saw the very curious flower of Canna; I should say the pollen was deposited where it is to prevent inevitable self-fertilisation. More Letters of Charles Darwin — Volume 2 The flowers of the common cabbage are adapted, as shown by H. Muller, for cross-fertilisation, and should this fail, for self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The most important of Darwin's work on floral biology is, however, that on cross and self-fertilisation, chiefly because it states the results of experimental investigations extending over many years. Darwin and Modern Science Nevertheless, the greater number likewise present structures which are manifestly adapted, though not in so striking a manner, for self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The Fumariaceae offer a good instance of this, and Treviranus threw this order in my teeth; but in Corydalis, Hildebrand shows how utterly false the idea of self-fertilisation is. Life and Letters of Charles Darwin — Volume 2 The Fumariaceae offer a good instance of this, and Treviranus threw this order in my teeth; but in Corydalis Hildebrand shows how utterly false the idea of self-fertilisation is. More Letters of Charles Darwin — Volume 2 So that there was very little difference in the number of seeds produced by cross-fertilisation and self-fertilisation, namely, as 100 to 92. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Darwin has himself demonstrated this for self-sterile plants, that is plants in which self-fertilisation produces no result. Darwin and Modern Science There are also various details of structure adapted for self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom I have also given reasons for believing that the inefficiency of a plant's own pollen is in most cases an incidental result, or has not been specially acquired for the sake of preventing self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Scott discusses the question of self-fertilisation at great length in a letter to Darwin dated April, and obviously written in 1863. More Letters of Charles Darwin — Volume 2 Professor Hoffman even maintains that the flowers of the kidney-bean are specially adapted for self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Nature thus tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation... Darwin and Modern Science He further remarks that the flowers which are rarely visited must be capable of self-fertilisation, otherwise they would quickly become extinct. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Nor is there any reason to doubt that many kinds of plants are capable under favourable circumstances of propagating themselves for very many generations by self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Darwin's caution to Scott was in some measure justified, for in his experiments on seedlings raised by self-fertilisation of the Edinburgh plants, he failed to confirm Scott's result. More Letters of Charles Darwin — Volume 2 When the varieties of Phaseolus vulgaris grow near one another in the open ground, they sometimes cross largely, notwithstanding their capacity for self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom In the first place the question is, whether or not the opinion expressed in the Orchid book that there is "Something injurious" connected with self-fertilisation, has been confirmed. Darwin and Modern Science Notwithstanding the several considerations just advanced, it seems to me highly improbable that plants bearing small and inconspicuous flowers have been or should continue to be subjected to self-fertilisation for a long series of generations. Effects of Cross and Self Fertilisation in the Vegetable Kingdom It cannot be admitted, under our present state of knowledge, that self-fertilisation continued during many successive generations is ever the most beneficial method of reproduction. Effects of Cross and Self Fertilisation in the Vegetable Kingdom A short note describing Cruger's discovery of self-fertilisation in Cattleya, Epidendrum, etc., and referring to the work of "an excellent observer, Mr. J. Scott." More Letters of Charles Darwin — Volume 2 Almost everyone who has studied the structure of papilionaceous flowers has been convinced that they are specially adapted for cross-fertilisation, although many of the species are likewise capable of self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom We can, at all events, affirm that Darwin adhered in essentials to his original position; but self-fertilisation afterwards assumed a greater importance than it formerly possessed. Darwin and Modern Science This latter evil, the greatest of all to any organism, would have been much lessened by their becoming hermaphrodites, though with the contingent disadvantage of frequent self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Cross-fertilisation proved to be beneficial, and self-fertilisation injurious. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Allied species differ greatly in the means by which cross-fertilisation is favoured and self-fertilisation avoided. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The purple-flowered plants were thrown away, as they might possibly have been the product of the accidental self-fertilisation of the mother-plant, owing to the castration not having been effectual. Effects of Cross and Self Fertilisation in the Vegetable Kingdom We may describe the objections which are based on the widespread occurrence of self-fertilisation and geitonogamy as of little importance. Darwin and Modern Science Close correspondence between the effects of cross-fertilisation and self-fertilisation, and of the legitimate and illegitimate unions of heterostyled plants, in comparison with hybrid unions. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The first and most important of the conclusions which may be drawn from the observations given in this volume, is that cross-fertilisation is generally beneficial, and self-fertilisation injurious. Effects of Cross and Self Fertilisation in the Vegetable Kingdom With respect to the second of these two propositions, namely, that self-fertilisation is generally injurious, we have abundant evidence. Effects of Cross and Self Fertilisation in the Vegetable Kingdom It follows also from the foregoing facts that the several varieties of the sweet-pea must have propagated themselves in England by self-fertilisation for very many generations, since the time when each new variety first appeared. Effects of Cross and Self Fertilisation in the Vegetable Kingdom These alone become weaker by self-pollination; while pure species derive no advantage from crossing and no disadvantage from self-fertilisation. Darwin and Modern Science In neither of these cases were any of the plants the product of self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom We may therefore conclude that the above two propositions are true,—that cross-fertilisation is generally beneficial and self-fertilisation injurious to the offspring. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Whether the evil from self-fertilisation goes on increasing during successive generations is not as yet known; but we may infer from my experiments that the increase if any is far from rapid. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Most of the varieties, however, endure for a shorter period; and this may be in part due to their weakness of constitution from long-continued self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The fixed forms of this plant, such as Hero, which was produced by self-fertilisation, and a form of Mimulus with white flowers spotted with red probably resulted from splitting of the hybrids. Darwin and Modern Science After plants have been propagated by self-fertilisation for several generations, a single cross with a fresh stock restores their pristine vigour; and we have a strictly analogous result with our domestic animals. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Ophrys offers a remarkable instance of one species having its structure manifestly adapted for self-fertilisation, and other species as manifestly adapted for cross-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Some species exist under two forms, the one bearing conspicuous flowers adapted for cross-fertilisation, the other bearing inconspicuous flowers adapted for self-fertilisation, whilst other species in the same genus present only a single form. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Nevertheless these plants produced plenty of seed, as they likewise did when covered by a net; they are therefore fully capable of self-fertilisation, and have probably been self-fertilised in this country for many generations. Effects of Cross and Self Fertilisation in the Vegetable Kingdom But the characters which hybrids exhibit on self-fertilisation are rather variable. Darwin and Modern Science If, as there is reason to suspect, self-fertilisation is in some respects beneficial, although more than counterbalanced by the advantages derived from a cross with a fresh stock, the problem becomes still more complicated. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The effects of cross- and self-fertilisation may be confined either to the growth or to the fertility of the offspring, but generally extends to both qualities. Effects of Cross and Self Fertilisation in the Vegetable Kingdom And secondly, that the injury from self-fertilisation follows from the want of such differentiation in the sexual elements. Effects of Cross and Self Fertilisation in the Vegetable Kingdom It should be especially observed that none of the plants of either lot were the product of self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Darwin succeeded in showing that in most of the orchids examined self-fertilisation is either an impossibility, or, under natural conditions, occurs only exceptionally. Darwin and Modern Science As some kinds of plants suffer much more from self-fertilisation than do others, so it probably is with animals from too close interbreeding. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Darwin, C., self-fertilisation in Pisum sativum. sexual affinities. on Primula. bud variation. constitutional vigour from cross parentage in common pea. hybrids of Gladiolus and Cistus. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Nemophila insignis. measurements. early flowering of crossed plant. effects of cross and self-fertilisation. seeds. Effects of Cross and Self Fertilisation in the Vegetable Kingdom However this may have been, it became, through continued self-fertilisation and the cultivation of the plants under uniform conditions, perfectly constant, to the exclusion of every other variety. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Objections which are based on the proof of the prevalence of self-fertilisation are not, therefore, pertinent. Darwin and Modern Science Structure of plants adapted to cross and self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom In 1862 I summed up my observations on Orchids by saying that nature "abhors perpetual self-fertilisation." Effects of Cross and Self Fertilisation in the Vegetable Kingdom We are therefore driven to the suspicion, which we shall soon see strengthened, that Hero transmitted to its offspring a peculiar constitution adapted for self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The present chapter is devoted to the Fertility of plants, as influenced by cross-fertilisation and self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Between self-sterility and reduced fertility as the result of self-fertilisation there is probably no fundamental difference. Darwin and Modern Science But as we shall presently see that a similar experiment made after two additional generations of self-fertilisation gave a different result, I know not how far to trust the present one. Effects of Cross and Self Fertilisation in the Vegetable Kingdom No attention was at first paid to it, and I know not how far it was at first used either for crossing or self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom This excess of height may be attributed not only to this variety naturally growing taller than the other plants, but to its possessing a peculiar constitution, so that it did not suffer from continued self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The Primulaceae seem eminently liable to suffer in fertility from self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom In only a few of the orchids investigated by Darwin—other similar cases have since been described—was self-fertilisation found to occur regularly or usually. Darwin and Modern Science The covered plant was occasionally shaken with violence, so as to imitate the effects of a gale of wind, and thus to facilitate as far as possible self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom This excellent observer remarks that, as the stigma lies between the anthers and is mature at the same time with them, self-fertilisation is possible. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The present species, therefore, does not seem so well fitted for self-fertilisation as most of the others. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Fritz Muller tried both kinds of self-fertilisation in the case of Bignonia, Tabernaemontana and Abutilon, likewise with no difference in the result. Effects of Cross and Self Fertilisation in the Vegetable Kingdom But he held the view, and that was, indeed, the natural assumption, that self-fertilisation usually occurs in a flower, in other words that the pollen of a flower reaches the stigma of the same flower. Darwin and Modern Science The fairest ratio, therefore, for the number of seeds produced by a cross and by spontaneous self-fertilisation is as 100 to 59. Effects of Cross and Self Fertilisation in the Vegetable Kingdom I was therefore often forced to use for self-fertilisation pollen from the same plant instead of from the same flower. Effects of Cross and Self Fertilisation in the Vegetable Kingdom But on two occasions, when I attended to this point, I was not able to detect any marked difference in the number of seeds produced by these two forms of self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Nevertheless, the belief that self-sterility is a quality which has been gradually acquired for the special purpose of preventing self-fertilisation must, I believe, be rejected. Effects of Cross and Self Fertilisation in the Vegetable Kingdom It was an accidental observation which inspired Darwin's experiments on the effect of cross and self-fertilisation. Darwin and Modern Science Analogous cases with Mimulus and Ipomoea, after several generations of self-fertilisation, have been already given. Effects of Cross and Self Fertilisation in the Vegetable Kingdom As the flowers are much frequented by Thrips, the self-fertilisation of most of the flowers under the net may have been due to the action of these minute insects. Effects of Cross and Self Fertilisation in the Vegetable Kingdom There was no uniform and marked difference in the number of seeds obtained from these two modes of self-fertilisation, both of which were illegitimate. Effects of Cross and Self Fertilisation in the Vegetable Kingdom But the strongest argument against the belief that self-sterility has been acquired to prevent self-fertilisation, is the immediate and powerful effect of changed conditions in either causing or in removing self-sterility. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Dr. Dickie and Professor Faivre state that the flowers are fertilised in the bud, and that self-fertilisation is inevitable. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Hildebrand has shown in the paper referred to under the last species, that this hermaphrodite grass is better adapted for cross-fertilisation than for self-fertilisation. Effects of Cross and Self Fertilisation in the Vegetable Kingdom Bearing all these circumstances in mind, it may be admitted that we have a fair basis for judging of the comparative effects of cross-fertilisation and of self-fertilisation on the growth of the offspring. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The slightly greater difference in height in this latter case, may possibly be attributed to the deteriorating effects of self-fertilisation carried on for two additional generations. Effects of Cross and Self Fertilisation in the Vegetable Kingdom The self-fertility of Primula veris increased after several generations of illegitimate fertilisation, which is a process closely analogous to self-fertilisation, but only as long as the plants were cultivated under the same favourable conditions. Effects of Cross and Self Fertilisation in the Vegetable Kingdom |
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