The Origin of Floral Structures Through Insect and Other AgenciesK. Paul, Trench, 1888 - 349 páginas |
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The Origin of Floral Structures Through Insect and Other Agencies George Henslow Vista completa - 1888 |
The Origin of Floral Structures Through Insect and Other Agencies George Henslow Vista completa - 1893 |
Términos y frases comunes
4-merous flowers adaptation to insect adhesion alternate leaves androecium anemophilous anthers appear arise arrangement arrested atrophy axial axis become bracts branches calyx carpellary carpels cause cells chorisis cleistogamous cohesion colour condition corolla correlated crossed cycle cylinder Darwin Dicotyledons differentiated dorsal cords epidermis Epilobium fact fertilisation fibro-vascular cords filaments five floral symmetry floral whorls foliage Forms of Flowers genera genus hermaphrodite heterostyled honey hypertrophy inferior ovary insect insect agency instances intercrossing irregular flowers irritation Labiata latter leaf long-styled male Monocotyledons Müller nectaries normally observed occur opposite leaves Orchids organs origin ovules papillæ pedicel Pelargonium perianth petaline petals petioles phyllotaxis pistil placentas plants pollen position posterior Primula produced protandrous protogynous protoplasm radial receptacular tube regard regular result seeds seen self-fertilisation sepaline sepals sepals and petals short-styled showing side species spiral stamens stigmas structure style superposed Teratology Tieghem tion tissue union usually visited whorls zygomorphic
Pasajes populares
Página v - With respect to the means of modification, he attributed something to the direct action of the physical conditions of life, something to the crossing of already existing forms, and much to use and disuse, that is, to the effects of habit.
Página 316 - Eschscholtzia, which are sterile with their own pollen, but fertile with that from any other individual. These several plants must therefore have been crossed during a long series of previous generations, and the artificial crosses in my experiments cannot have increased the vigour of the offspring beyond that of their progenitors. Therefore the difference between the self-fertilised and crossed plants raised by me cannot be attributed to the superiority of the crossed, but to the inferiority of...
Página 1 - Much has been written on the structure of flowers, and it might seem almost superfluous to attempt to say anything more on the subject, but it is only within the last few years that a new literature has sprung up, in which the authors have described their observations and given their interpretations of the uses of floral mechanisms, more especially in connection with the processes of fertilization.
Página 315 - ... that cross-fertilisation is generally beneficial, and self-fertilisation injurious. This is shown by the difference in height, weight, constitutional vigour, and fertility of the offspring from crossed and self-fertilised flowers, and in the number of seeds produced by the parent-plants. With respect to the second of these two propositions, namely, that self-fertilisation is generally injurious, we have abundant evidence.
Página 321 - ... seeds per capsule. Thus the proportional number of seeds per capsule produced by the plants of crossed origin to those produced by the plants of self-fertilised origin (both lots being spontaneously self-fertilised) was as 100 to 125. This anomalous result is probably due to some of the self-fertilised plants having varied so as to mature their pollen and stigmas more nearly at the same time than is proper to the species ; and we have already seen that some plants in the 7 No.
Página xi - My object is to endeavour to refer every part of the structures of flowers to some one or more definite causes arising from the environment taken in its widest sense.
Página 325 - There was no great difference in the number of flowers and capsules produced by the two lots, when both were left freely exposed to the visits of insects.
Página 311 - ... variety, or at least from another flower, rather than with its own ; and as races of animals are known to degenerate, if they are perpetuated by the union of near kindred, it seems not unlikely that vigour may be given also to any race of vegetables by introducing a cross, though of the same kind, and especially from an individual grown in a different soil or aspect.
Página 311 - I am inclined to think that I have derived advantage from impregnating the flower, from which I wished to obtain seed, with pollen from another individual of the same variety, or at least from another flower, rather than with its own...
Página viii - ... and he adds .-—"According to my view, transmutation by purely internal causes is not to be entertained. If we could absolutely suspend the changes of the external conditions of life, existing species would remain stationary. The action of external inciting causes, in the widest sense of the word, is alone able to produce modifications...