| → bring 1866 1869 |
| no doubt bring 1872 |
|
| → forms of doubtful value. 1866 1869 |
| them. 1872 |
|
| → as 1866 1869 |
| by other botanists to be 1872 |
|
| ↑ 4 blocks not present in 1866 1869 1872; present in 1859 1860 1861 |
| I will here give only a single instance,— the well-known one of the primrose and cowslip, or Primula veris
and elatior.
These plants differ considerably in appearance; they have a different flavour
and emit a different odour; they flower at slightly different periods; they grow in somewhat different stations; they ascend mountains to different heights; they have different geographical ranges; and lastly, according to very numerous experiments made during several years by that most careful observer Gärtner, they can be crossed only with much difficulty.
We could hardly wish for better evidence of the two forms being specifically distinct.
On the other hand, they are united by many intermediate links, and it is very doubtful whether these links are hybrids; and there is, as it seems to me, an overwhelming
amount of experimental evidence, showing that they descend from common parents, and consequently must be ranked as varieties.
|
|
| → of course are not of 1866 1869 |
| are not of course of 1872 |
|
|
Close investigation, in many cases, will
→bring
naturalists to
how to rank doubtful forms. Yet it must be confessed that
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
his attention, varieties of it will almost universally be found recorded. These varieties, moreover, will often be 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 almost universally 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. ↑
|
|
| I may here allude to a remarkable memoir lately published by A. de Candolle, on the oaks of the whole world. No one ever had more ample materials for the discrimination of the species, or could have worked on them with more zeal and sagacity. He first gives in detail all the many points of structure which vary in the
and estimates numerically the relative frequency of the variations. He specifies above a dozen characters which may be found varying even on the same branch, sometimes according to age or development, sometimes without any assignable reason. Such characters
→of course are not of
specific value, but they are, as Asa Gray has remarked in commenting on this memoir, such as generally enter into specific definitions. De Candolle then goes on to say that he gives the rank of species to the forms that differ by characters never varying on the same tree, and never found connected by intermediate states. After this discussion, the result of
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