and treated in every respect alike, as well as the extraordinary
superiority of the self-fertilised over the crossed plants in the first
generation, considered together, make me believe that some individuals
of the present species differ to a certain extent from others in their
sexual affinities (to use the term employed by Gartner), like closely
allied species of the same genus. Consequently if two plants which thus
differ are crossed, the seedlings suffer and are beaten by those from
the self-fertilised flowers, in which the sexual elements are of the
same nature. It is known that with our domestic animals certain
individuals are sexually incompatible, and will not produce offspring,
although fertile with other individuals. (6/3. I have given evidence on
this head in my 'Variation of Animals and Plants under Domestication'
chapter 18 2nd edition volume 2 page 146.) But Kolreuter has recorded a
case which bears more closely on our present one, as it shows that in
the genus Nicotiana the varieties differ in their sexual affinities.
(6/4. 'Das Geschlecht der Pflanzen, Zweite Fortsetzung' 1764 pages
55-60.) He experimented on five varieties of the common tobacco, and
proved that they were varieties by showing that they were perfectly
fertile when reciprocally crossed; but one of these varieties, if used
either as the father or the mother, was more fertile than any of the
others when crossed with a widely distinct species, N. glutinosa. As the
different varieties thus differ in their sexual affinities, there is
nothing surprising in the individuals of the same variety differing in a
like manner to a slight degree.

Taking the plants of the three generations altogether, the crossed show
no superiority over the self-fertilised, and I can account for this fact
only by supposing that with this species, which is perfectly
self-fertile without insect aid, most of the individuals are in the same
condition, as those of the same variety of the common pea and of a few