asked, will suffice? if that between America and Europe is ample, will
that between the Continent and the Azores, or Madeira, or the Canaries,
or Ireland, be sufficient? It must be admitted that many forms,
considered by highly-competent judges as varieties, have so perfectly
the character of species that they are ranked by other highly-competent
judges as good and true species. But to discuss whether they are
rightly called species or varieties, before any definition of these
terms has been generally accepted, is vainly to beat the air.
Many of the cases of strongly-marked varieties or doubtful species well
deserve consideration; for several interesting lines of argument, from
geographical distribution, analogical variation, hybridism, etc., have
been brought to bear on the attempt to determine their rank. 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 Gartner, 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.
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
44