They consisted of ten females and of a single hermaphrodite. Whether or not the conditions to which they had been subjected caused the great excess of females I do not know. In the females the pistil is rather longer than that of the hermaphrodite, and the stamens are mere rudiments, with minute colourless anthers destitute of pollen. The windows of the greenhouse were left open, and the flowers were incessantly visited by humble and hive bees. Although the ten females did not produce a single grain of pollen, yet they were all thoroughly well fertilised by the one hermaphrodite plant, and this is an interesting fact. It should be added that no other plant of this species grew in my garden. The seeds were collected from the finest female plant, and they weighed 78 grains; whilst those from the hermaphrodite, which was a rather larger plant than the female, weighed only 33.2 grains; that is, in the ratio of 100 to 43. The female form, therefore, is very much more fertile than the hermaphrodite, as in the two last cases; but the hermaphrodite was necessarily self-fertilised, and this probably diminished its fertility.
We may now consider the probable means by which so many of the Labiatae have been separated into two forms, and the advantages thus gained. H. Muller supposes that originally some individuals varied so as to produce more conspicuous flowers; and that insects habitually visited these first, and then dusted with their pollen visited and fertilised the less conspicuous flowers. (7/17. 'Die Befruchtung der Blumen' pages 319, 326.) The production of pollen by the latter plants would thus be rendered superfluous, and it would be advantageous to the species that their stamens should abort, so as to save useless expenditure. They would thus be converted into females. But another view may be suggested: as the production of a large supply of seeds evidently is of high importance to many plants, and as we have seen in the three foregoing cases that the females produce many more seeds than the hermaphrodites, increased fertility seems to me the more probable cause of the formation and separation of the two forms. From the data above given it follows that ten plants of Thymus serpyllum, if half consisted of hermaphrodites and half of females, would yield seeds compared with ten hermaphrodite plants in the ratio of 100 to 72. Under similar circumstances the ratio with Satureia hortensis (subject to the doubt from the self-fertilisation of the hermaphrodite) would be as 100 to 60. Whether the two forms originated in certain individuals varying and producing more seed than usual, and consequently producing less pollen; or in the stamens of certain individuals tending from some unknown cause to abort, and consequently producing more seed, it is impossible to decide; but in either case, if the tendency to the increased production of seed were steadily favoured, the result would be the complete abortion of the male organs. I shall presently discuss the cause of the smaller size of the female corolla.
[Scabiosa arvensis (DIPSACEAE).
It has been shown by H. Muller that this species exists in Germany under an hermaphrodite and female form. (7/18. 'Die Befruchtung der Blumen' page 368. The two forms occur not only in Germany, but in England and France. Lecoq 'Geographie Bot.' 1857 tome 6 pages 473, 477, says that male plants as well as hermaphrodites and females coexist; it is, however, possible that he may have been deceived by the flowers being so strongly proterandrous. From what Lecoq says, S. succisa likewise appears to occur under two forms in France.) In my neighbourhood (Kent) the female plants do not nearly equal in number the hermaphrodites. The stamens of the females vary much in their degree of abortion; in some plants they are quite short and produce no pollen; in others they reach to the mouth of the corolla, but their anthers are not half the proper size, never dehisce, and contain but few pollen-grains, these being colourless and of small diameter. The hermaphrodite flowers are strongly proterandrous, and H.