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Show 112 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. pollen in the same manner from othe~ .long-sty led plants, and were thus illegitimately fertilised. They produced 14 seeds, or only 4 · 66 per flower-head. Two flower-heads on short-styled plants received pollen in like manner from long-sty led flowers, and were thus legitimately fertilised. They produced 8 seeds, or 4 per flower-head. Fig. 7. Upper figure, the long-styled form; lower figure, the short-styled. Some of the anthers have dehisced, others have not. POLYGONUM FAGOPYRUM. (From H. MUller.) Four heads on short-styled plants similarly received pollen from other short-styled plants, and were thus illegitimately fertilised, They produced 9 seeds, or 2 · 25 per flower-head. The results from fertilising the flower-heads in the above imperfect manner cannot be fully trusted; but I may state that the four legitimately fertilised flower- CHAP. III. POLYGONUM FAGOPYRUM. 113 heads yielded on an average 7 ·50 seeds per head; whereas the seven illegitimately fertilised heads yielded less than half the number, or on an averao-e 5 only 3 · 28 seeds. The legitimately crossed seeds from the long-sty led 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. 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 ~enus, contains, as far as is at present known, only a Single heterostyled species, namely the present one. H. Muller in his interesting description of several * 'Die Befruchtung,' &c., p. 175, and' Nature,' Jan. 1, 1874, p. 166. I |