rm is considered by the highest authority,
M. Gay, to be merely a strongly marked race of _F. Chiloensis_.[715]
These five or six forms have been ranked by most botanists as
specifically distinct; but this may be doubted, for Andrew Knight,[716]
who raised no less than 400 crossed strawberries, asserts that the _F.
Virginiana_, _Chiloensis_, and _grandiflora_ "may be made to breed
together indiscriminately," and he found, in accordance with the
principle of analogous variation, "that similar varieties could be
obtained from the seeds of any one of them."

Since Knight's time there is abundant and additional evidence[717] of
the extent to which the American forms spontaneously cross. We owe
{352} indeed to such crosses most of our choicest existing varieties.
Knight did not succeed in crossing the European wood-strawberry with
the American Scarlet or with the Hautbois. Mr. Williams, of Pitmaston,
however, succeeded; but the hybrid offspring from the Hautbois, though
fruiting well, never produced seed, with the exception of a single one,
which reproduced the parent hybrid form.[718] Major E. Trevor Clarke
informs me that he crossed two members of the Pine class (Myatt's B.
Queen and Keen's Seedling), with the wood and hautbois, and that in
each case he raised only a single seedling; one of these fruited, but
was almost barren. Mr. W. Smith, of York, has raised similar hybrids
with equally poor success.[719] We thus see[720] that the European and
American species can with some difficulty be crossed; but it is
improbable that hybrids sufficiently fertile to be worth cultivation
will ever be thus produced. This fact is surprising, as these forms
structurally are not widely distinct, and are sometimes connected in
the districts where they grow wild, as I hear from Professor Asa Gray,
by puzzling intermediate forms.

The energetic culture of the strawberry is of recent date, and the
cultivated varieties can in most cases still be classed under some one
of the above five native stocks. As the American strawberries cross so
freely and spontaneously, we can hardly doubt that they will ultimately
become inextricably confused. We find, indeed, that horticulturists at
present disagree under which class to rank some few of the varieties;
and a writer in the 'Bon Jardinier' of 1840 remarks that formerl