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Show • 142 HETEROSTYLED TRIMORPHIC PLANTS. CHAP. IV. thers. The e~d of the pistil is generally bent upwards at right angles. The six longest stamens, with their pink filaments and green pollen, resemble the corresponding stan1ens of the mrd-styl~d form. ~ut according to H. Muller, their pollen-g:arns. are a httle larg~r, viz. 9!-10~, instead of 9-10 rn drameter. The six mid-leno-th sta1nens, with their uncoloured filaments and yellow pollen, resemble in the size of their poll.engrains and in all other respects the corresponding stamens of the long-styled form. The difference in diameter between the grains from the two sets of anthers in the short-styled forn1 is as 100 to 73. The capsules contain fewer seeds on an average than those of either of the preceding forrns, na1nely 83 · 5; and the seeds are considerably smaller. In this latter respect, but not in number, there i~ ~ gradation parallel to that in the length of the prs.trl, the longstyled having the largest seeds, the mid-styled the next in size, and the short-sty led the smallest. We thus see that this plant exists under three female forms, which differ in the length and c:uvature of the style, in the size and state of the stigma, and in the number and size of the seed. There are altoo-ether thirty-six males or stamens, and these can be divided into three sets of a dozen each, differing from one another in length, curvature, and colour of the filaments-in the size of the anthers, and especially in the colour and diameter of the pollen-grains. Each form bears half-a-dozen of one kind of stamens and half-a-dozen of another kind, but not all three kinds. The three kinds of · stamens correspond in length with the three pistils: the correspondence is always bet~ee~ half of the stamens in two of the forms with the pistil of the third form. The following table of the diameters of the pollen-grains, after imn1ersion in water, from CHAP. IV. L YTHRUM SALICARIA. 143 both sets of stamens in all three forms is copied from H. M iiller ; they are arranged in the order of their SIZe:- Pollen-grains from longest stamens of short-sty led form , , , , mid-styled , , , rr:tid-length stamens of long-sty led , , , , , short-sty led , , , shortest stamens of long-styled , , , , , mid-sty led , 9f to 10~ 9 " 10 7 " 7~ 7 " 7~ 6 " 6! 6 " 6 We here see that the largest pollen-grains come from the longest stamens, and the least from tho shortest · the extreme difference in diameter between them' being as 100 to 60. The average number of seeds in the three forms was ascertained by counting them in eight fine selected capsules taken from plants growing wild, and the result was, as we have seen, for the long-styled (neglecting decimals) 93, mid-styled 130, and short-styled 83. I should not have trusted in these ratios had I not possessed a number of plants in my garden which, owing to their youth, did not yield tho full coinplement of seed, but were of the same age and grew under the same conditions, and were fre ly visited by bees. I took six fine capsules from each, and found the average to be for the long-styled 80, for the midstyled 97, and for the short-styled 61. Lastly, legitimate unions effected by me between the three forms gave, as may be seen in the following tables, for the long-styled an average of 90 seeds, for the mid-styled 117, and for the short-styled 71. So that we have good concurrent evidence of a difference in the average production of seed by the three forms. To show that the unions effected by me often produced their full effect and may be trusted, I may state that one midstyled capsule yielded 151 good seeds, which is the same number as in the finest wild capsule which I |