The excess may be attributed to the plants having been grown separately in good
soil. With respect to the illegitimate unions, we shall best appreciate their
degree of lessened fertility by the following facts. Gartner estimated the
sterility of the unions between distinct species, in a manner which allows of a
strict comparison with the results of the legitimate and illegitimate unions of
Primula. (1/6. 'Versuche uber die Bastarderzeugung' 1849 page 216.) With P.
veris, for every 100 seeds yielded by the two legitimate unions, only 64 were
yielded by an equal number of good capsules from the two illegitimate unions.
With P. Sinensis, as we shall hereafter see, the proportion was nearly the same-
-namely, as 100 to 62. Now Gartner has shown that, on the calculation of
Verbascum lychnitis yielding with its own pollen 100 seeds, it yielded when
fertilised by the pollen of Verbascum Phoeniceum 90 seeds; by the pollen of
Verbascum nigrum, 63 seeds; by that of Verbascum blattaria, 62 seeds. So again,
Dianthus barbatus fertilised by the pollen of D. superbus yielded 81 seeds, and
by the pollen of D. japonicus 66 seeds, relatively to the 100 seeds produced by
its own pollen. We thus see--and the fact is highly remarkable--that with
Primula the illegitimate unions relatively to the legitimate are more sterile
than crosses between distinct species of other genera relatively to their pure
unions.
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