The six mid-length stamens project about two-thirds the length of the pistil, and correspond in length with the pistil of the mid-styled form. Such correspondence in this and the two following forms is generally very close; the difference, where there is any, being usually in a slight excess of length in the stamens. The six shortest stamens lie concealed within the calyx; their ends are turned up, and they are graduated in length, so as to form a double row. The anthers of these stamens are smaller than those of the mid-length ones. The pollen is of the same yellow colour in both sets. H. Muller measured the pollen-grain in all three forms, and his measurements are evidently more trustworthy than those which I formerly made, so I will give them. (4/2. 'Die Befruchtung der Blumen' 1873 page 193.) The numbers refer to divisions of the micrometer equalling 1/300 millimetres. The grains, distended with water, from the mid-length stamens are 7 to 7 1/2, and those from the shortest stamens 6 to 6 1/2 in diameter, or as 100 to 86. The capsules of this form contain on an average 93 seeds: how this average was obtained will presently be explained. As these seeds, when cleaned, seemed larger than those from the mid-styled or short-styled forms, 100 of them were placed in a good balance, and by the double method of weighing were found to equal 121 seeds of the mid-styled or 142 of the short-styled; so that five long-styled seeds very nearly equal six mid-styled or seven short-styled seeds.
MID-STYLED FORM.
The pistil occupies the position represented in Figure 4.10, with its extremity considerably upturned, but to a variable degree; the stigma is seated between the anthers of the longest and the shortest stamens. The six longest stamens correspond in length with the pistil of the long-styled form; their filaments are coloured bright pink; the anthers are dark-coloured, but from containing bright-green pollen and from their early dehiscence they appear emerald-green. Hence in general appearance these stamens are remarkably dissimilar from the mid-length stamens of the long-styled form. The six shortest stamens are enclosed within the calyx, and resemble in all respects the shortest stamens of the long-styled form; both these sets correspond in length with the short pistil of the short-styled form. The green pollen-grains of the longest stamens are 9 to 10 in diameter, whilst the yellow grains from the shortest stamens are only 6; or as 100 to 63. But the pollen-grains from different plants appeared to me, in this case and others, to be in some degree variable in size. The capsules contain on an average 130 seeds; but perhaps, as we shall see, this is rather too high an average. The seeds themselves, as before remarked, are smaller than those of the long-styled form.
SHORT-STYLED FORM.
The pistil is here very short, not one-third of the length of that of the long- styled form. It is enclosed within the calyx, which, differently from that in the other two forms, does not enclose any anthers. The end of the pistil is generally bent upwards at right angles. The six longest stamens, with their pink filaments and green pollen, resemble the corresponding stamens of the mid-styled form. But according to H. Muller, their pollen-grains are a little larger, namely 9 1/2 to 10 1/2, instead of 9 to 10 in diameter. The six mid-length stamens, with their uncoloured filaments and yellow pollen, resemble in the size of their pollen-grains 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 form is as 100 to 73. The capsules contain fewer seeds on an average than those of either of the preceding forms, namely 83.5; and the seeds are considerably smaller. In this latter respect, but not in number, there is a gradation parallel to that in the length of the pistil, the long-styled having the largest seeds, the mid-styled the next in size, and the short-styled the smallest.
We thus see that this plant exists under three female forms, which differ in the length and curvature of the style, in the size and state of the stigma, and in the number and size of the seed.