The class of facts now adduced must certainly be held to prove that in
many large genera and in some single species there is a very large
amount of variation, which renders it quite impossible for experts to
agree upon the limits of species. We will now adduce a few striking
cases of individual variation.
The distinguished botanist, Alp. de Candolle, made a special study of
the oaks of the whole world, and has stated some remarkable facts as to
their variability. He declares that on the same branch of oak he has
noted the following variations: (1) In the length of the petiole, as one
to three; (2) in the form of the leaf, being either elliptical or
obovoid; (3) in the margin being entire, or notched, or even pinnatifid;
(4) in the extremity being acute or blunt; (5) in the base being sharp,
blunt, or cordate; (6) in the surface being pubescent or smooth; (7) the
perianth varies in depth and lobing; (8) the stamens vary in number,
independently; (9) the anthers are mucronate or blunt; (10) the fruit
stalks vary greatly in length, often as one to three; (11) the number of
fruits varies; (12) the form of the base of the cup varies; (13) the
scales of the cup vary in form; (14) the proportions of the acorns vary;
(15) the times of the acorns ripening and falling vary.
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