er from experiments tried on a much
larger scale. In the second place Mr. Scott experimented on the
relative fertility of unions between similarly and
dissimilarly-coloured varieties of the same species. Thus he fertilised
six flowers of the yellow variety of _V. lychnitis_ by its own pollen,
and obtained six capsules, and calling, for the sake of having a
standard of comparison, the average number of good seed in each one
hundred, he found that this same yellow variety, when fertilised by the
white variety, yielded from seven capsules an average of ninety-four
seed. On the same principle, the white variety of _V. lychnitis_ by its
own pollen (from six capsules), and by the pollen of the yellow variety
(eight capsules), yielded seed in the proportion of 100 to 82. The
yellow variety of _V. thapsus_ by its own pollen (eight capsules), and
by that of the white variety (only two capsules), yielded seed in the
proportion of 100 to 94. Lastly, the white variety of _V. blattaria_ by
its own pollen (eight capsules), and by that of the yellow variety
(five capsules), yielded seed in the proportion of 100 to 79. So that
in every case the unions of dissimilarly-coloured varieties of the same
species were less fertile than the unions of similarly-coloured
varieties; when all the cases are grouped together, the difference of
fertility is as 86 to 100. Some additional trials were made, and
altogether thirty-six similarly-coloured unions yielded thirty-five
good {107} capsules; whilst thirty-five dissimilarly-coloured unions
yielded only twenty-six good capsules. Besides the foregoing
experiments, the purple _V. phoeniceum_ was crossed by a rose-coloured
and a white variety of the same species; these two varieties were also
crossed together, and these several unions yielded less seed than _V.
phoeniceum_ by its own pollen. Hence it follows from Mr. Scott's
experiments, that in the genus Verbascum the similarly and
dissimilarly-coloured varieties of the same species behave, when
crossed, like closely allied but distinct species.[229]

This remarkable fact of the sexual affinity of similarly-coloured
varieties, as observed by Gaertner and Mr. Scott, may not be of very
rare occurrence; for the subject has not been attended to by others.
The following case is worth giving, partly to show how difficult it i