Origin of Species Variorum

→ when 1859 1860 1861 1866

than the other varieties, when 1869 1872

→ glutinosa. Hence the reproductive system of this one variety must have been in some manner and in some degree modified. 1861

glutinosa. 1859 1860 1866 1869 1872

↑ 1 blocks not present in 1861; present in 1859 1860 1866 1869 1872

Hence the reproductive system of this one variety must have been in some manner and in some degree modified.

→ from 1859 1860 1861 1866

it cannot be maintained that varieties when crossed are invariably quite fertile;—from 1869

it can no longer be maintained that varieties when crossed are invariably quite fertile. From 1872

→ infertile 1859 1860 1861

proved to be infertile 1866 1869 1872

→ species; from man selecting only 1859 1860 1861

a species; from man selecting only 1866

a species;—from man attending only to 1869

a species;— from man attending only 1872

→ the production of the most distinct 1859 1860 1861

his 1866 1869 1872

→ not wishing or being able to produce recondite and functional differences in the reproductive system; from 1859 1860 1861

not wishing or being able to produce recondite and functional differences in their reproductive systems; from 1866

such varieties not having been exposed for a very long period to uniform conditions of life;—from 1869

such varieties not having been exposed for very long periods to uniform conditions of life;— from 1872

→ and facts, I do not think that the very general fertility of varieties can be proved either to be of universal occurrence, or to form 1861

and facts, I do not think that the very general fertility of varieties can be proved to be of universal occurrence, or to form 1859 1860

and facts, I do not think that the fertility of varieties can be proved either to be of universal occurrence, or to form 1866

we may conclude that fertility does not constitute 1869 1872

→ species. 1859 1860 1861 1866

species when crossed. 1869 1872

→ varieties, considering how entirely ignorant we are on the causes of both fertility and sterility, does not seem to me sufficient to overthrow the view taken with respect to the very general, but not invariable, sterility of first crosses between species and of their hybrids, namely, that it is not 1861 1866

varieties does not seem to me sufficient to overthrow the view which I have taken with respect to the very general, but not invariable, sterility of first crosses and of hybrids, namely, that it is not 1859 1860

crossed species may safely be looked at not as 1869

crossed species may safely be looked at, not as 1872

→ endowment, but is 1859 1860 1861 1866

acquirement or endowment, but as 1869 1872

→ slowly acquired modifications, more especially in the reproductive systems of the forms which are crossed. 1859 1860 1861

modifications, slowly impressed, by unknown means, on the reproductive systems of the parent-forms. 1866

changes of an unknown nature in their sexual elements. 1869 1872

From

observations

experiments

which I have made on certain varieties of hollyhock, I am inclined to suspect that they present analogous facts.

Kölreuter, whose accuracy has been confirmed by every subsequent observer, has proved the remarkable fact, that one

particular variety

variety

of the common tobacco

was

fertile

fertile,

→when crossed with a widely distinct

species.

~~than~~

~~are~~

~~the~~

~~other~~

~~varieties.~~

experimentised

on five

forms

forms,

which are commonly reputed to be varieties, and which he tested by the severest trial, namely, by reciprocal crosses, and he found their mongrel offspring perfectly fertile. But one of these five varieties, when used either as

the father

father

or mother, and crossed with the Nicotiana glutinosa, always yielded hybrids not so sterile as those which were produced from the four other varieties when crossed with N. →glutinosa. Hence the reproductive system of this one variety must have been in some manner and in some degree modified. ↑

From these

facts

facts;

→from the great difficulty of ascertaining the infertility of varieties in a state of nature, for a supposed

variety,

variety

if →infertile in any

degree,

degree

would

almost universally

generally

be ranked as →species; from man selecting only

to external

external

characters in →the production of the most distinct domestic varieties, and from →not wishing or being able to produce recondite and functional differences in the reproductive system; from these several considerations →and facts, I do not think that the very general fertility of varieties can be proved either to be of universal occurrence, or to form a fundamental distinction between

them

varieties

and →species. The general

sterility

fertility

of →varieties, considering how entirely ignorant we are on the causes of both fertility and sterility, does not seem to me sufficient to overthrow the view taken with respect to the very general, but not invariable, sterility of first crosses between species and of their hybrids, namely, that it is not a special →endowment, but is incidental on →slowly acquired modifications, more especially in the reproductive systems of the forms which are crossed.