But, as we shall presently see, good evidence can be assigned for
ranking them as distinct. Owing to the doubts on this head, I tried whether the
two would mutually fertilise one another. Twelve short-styled flowers of P.
angustifolia were legitimately fertilised with pollen from long-styled plants of
P. officinalis (which, as we have just seen, are moderately self-fertile), but
they did not produce a single fruit. Thirty-six long-styled flowers of P.
angustifolia were also illegitimately fertilised during two seasons with pollen
from the long-styled P. officinalis, but all these flowers dropped off
unimpregnated. Had the plants been mere varieties of the same species these
illegitimate crosses would probably have yielded some seeds, judging from my
success in illegitimately fertilising the long-styled flowers of P. officinalis;
and the twelve legitimate crosses, instead of yielding no fruit, would almost
certainly have yielded a considerable number, namely, about nine, judging from
the results given in Table 3.20. Therefore P. officinalis and angustifolia
appear to be good and distinct species, in conformity with other important
functional differences between them, immediately to be described.
TABLE 3.20. Pulmonaria angustifolia.
Column 1: Nature of the Union.
Column 2: Number of Flowers fertilised.
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