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Dec. 3d 1862. The structure of animals and plants, many decisive experiments & common experience shows that good is derived from crossing one individual with another of a distinct family or race. — Now if for instance, pollen from a distinct plant produces more numerous & more vigourous seedlings, than flowers own pollen on the same stigma, then two pollen must certainly be in some slight degree differentiated. Hence some differentiation of pollen is commonest Phenomenon. — This differs under culture in So must the stigmas or ovules, for if pollen of 1st plant will be effective on the 2nd plant. — The differentiation of female organs in some plants is carried to extremes in certain plants under culture, whe as Lobelia, Crinum, &c. — Again We see & while thus see that dimorphism may readily arise & we can understand why so variable within same genus; how easily lost under culture as in P. Sinensis, & in structure

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in P. auricula & Siberica (see J. Scot list). But if we once admit, the d easy of differentiation of pollen, we can understand hybridity— P. Sinensis shows how this sterility affects offspring. — N. Selection only collect & favours this sterility— no doubt it is always in some degree correlated with changed structure. —