28 seeds. The legitimately crossed seeds from the long-styled
flowers were finer than those from the illegitimately fertilised flowers on the
same plants, in the ratio of 100 to 82, as shown by the weights of an equal
number.
About a dozen plants, including both forms, were protected under nets, and early
in the season they produced spontaneously hardly any seeds, though at this
period the artificially fertilised flowers produced an abundance; but it is a
remarkable fact that later in the season, during September, both forms became
highly self-fertile. They did not, however, produce so many seeds as some
neighbouring uncovered plants which were visited by insects. Therefore the
flowers of neither form when left to fertilise themselves late in the season
without the aid of insects, are nearly so sterile as most other heterostyled
plants. A large number of insects, namely 41 kinds as observed by H. Muller,
visit the flowers for the sake of the eight drops of nectar. (3/14. 'Die
Befruchtung' etc. page 175 and 'Nature' January 1, 1874 page 166.) He infers
from the structure of the flowers that insects would be apt to fertilise them
both illegitimately as well as legitimately; but he is mistaken in supposing
that the long-styled flowers cannot spontaneously fertilise themselves.
Differently to what occurs in the other genera hitherto noticed, Polygonum,
though a very large genus, contains, as far as is at present known, only a
single heterostyled species, namely the present one.
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