On the Origin of Species by Means of Natural SelectionJohn Murray, 1860 - 502 páginas |
Dentro del libro
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Página 15
... pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding quite freely under confinement ; and ...
... pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding quite freely under confinement ; and ...
Página 16
... pollen . But it is the opinion of most physiologists that there is no essential difference between a bud and an ovule in their earliest stages of for- mation ; so that , in fact , " sports " support my view , that variability may be ...
... pollen . But it is the opinion of most physiologists that there is no essential difference between a bud and an ovule in their earliest stages of for- mation ; so that , in fact , " sports " support my view , that variability may be ...
Página 71
... pollen- masses and thus to fertilise them . I have , also , reason to believe that humble - bees are indispensable to the fertilisa tion of the heartsease ( Viola tricolor ) , for other bees do not visit this flower . From experiments ...
... pollen- masses and thus to fertilise them . I have , also , reason to believe that humble - bees are indispensable to the fertilisa tion of the heartsease ( Viola tricolor ) , for other bees do not visit this flower . From experiments ...
Página 87
... pollen from flower to flower , would likewise be favoured or selected . We might have taken the case of insects visiting flowers for the sake of collecting pollen instead of nectar ; and as pollen is formed for the sole object of ...
... pollen from flower to flower , would likewise be favoured or selected . We might have taken the case of insects visiting flowers for the sake of collecting pollen instead of nectar ; and as pollen is formed for the sole object of ...
Página 88
... pollen , and a rudimentary pistil ; other holly - trees bear only female flowers ; these have a full - sized pistil , and four stamens with shrivelled anthers , in which not a grain of pollen can be detected . Having found a female tree ...
... pollen , and a rudimentary pistil ; other holly - trees bear only female flowers ; these have a full - sized pistil , and four stamens with shrivelled anthers , in which not a grain of pollen can be detected . Having found a female tree ...
Otras ediciones - Ver todas
The Origin of Species by Means of Natural Selection: The Descent of Man and ... Charles Darwin Vista de fragmentos - 1952 |
On the Origin of Species by Means of Natural Selection . Charles Darwin Sin vista previa disponible - 2019 |
the origin of species by means of natural selection the descent of man and ... charles darwin Sin vista previa disponible - 1952 |
Términos y frases comunes
accumulated adapted affinities allied species America amount ancient animals appear become bees believe birds breeds cause cells characters cirripedes climate closely allied colour continuous crossed crustaceans degree difficulty distinct species disuse divergence domestic doubt embryo endemic Europe existing exterminated extinct extremely facts favourable fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hermaphrodites hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate larvæ less living look males mammals manner migration modification modified descendants natural selection naturalists nearly nest offspring organic organisation paleozoic perfect pigeons pistil plants pollen present probably produced progenitor ranked reciprocal crosses remarked resemble rudimentary seeds seems sexual selection Silurian slight South America sterility structure struggle successive suppose swimbladder tend theory tion trees variability variation varieties vary whole widely