so much labour, he emphatically remarks: "They are mistaken, who repeat that the greater part of our species are clearly limited, and that the doubtful species are in a feeble minority. This seemed to be true, so long as a genus was imperfectly known, and
its
species were founded upon a few specimens, that is to say, were provisional. Just as we come to know them better, intermediate forms flow in, and doubts as to specific limits augment." He also adds that it is the best known species which present the greatest number of spontaneous varieties and sub-varieties. Thus Quercus robur has twenty-eight varieties, all of which, excepting six, are clustered round three sub-species, namely, Q. pedunculata, sessiliflora, and pubescens. The forms which connect these three sub-species are comparatively rare; and, as Asa Gray
remarks, | remarks, 1866 1869 | | again remarks, 1872 |
| wholly extinct, 1869 1872 | | extinct, 1866 |
| succession of forms is the 1866 1869 |
| OMIT 1872 |
| classification;" 1866 1869 | | classification." 1872 |
| adds, 1866 1869 | adds, 1872 |
| direct 1866 1869 | direct 1872 |
| proof 1866 1869 | proof 1872 |
| still 1866 1869 | still 1872 |
| wanting. 1866 1869 | wanting. 1872 |
| 5 blocks not present in 1866 1869 1872; present in 1859 1860 1861 | | Close investigation, in most cases, will bring naturalists to an agreement how to rank doubtful forms.
Yet it must be confessed,
that it is in the best-known countries that we find the greatest number of forms of doubtful value.
I have been struck with the fact, that if any animal or plant in a state of nature be highly useful to man, or from any cause closely attract his attention, varieties of it will almost universally be found recorded.
These varieties, moreover, will be often ranked by some authors as species.
Look at the common oak, how closely it has been studied; yet a German author makes more than a dozen species out of forms, which are very generally
considered as varieties; and in this country the highest botanical authorities and practical men can be quoted to show that the sessile and pedunculated oaks are either good and distinct species or mere varieties.
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