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Show 124 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. about the ratio of 100 to 62. The two forms of ..lE. mollis present a like difference in the length of their pistils and stamens. .LZEGIPHILA OBDURATA. Flowers of this bush were sent me fr01u St. Catharina in Brazil, by Fritz Muller, and were named for me at Kew. They appeared at first sight grandly heterostyled, as the stigma of the long-styled form projects far out of the corolla, whilst the anthers are seated halfway down within the tube; whereas in the short-styled form the anthers project from the corolla and the stigma is enclosed in the tube at nearly the same level with the anthers of the other form. The pistil of the long-styled is to that of the short-styled as 100 to 60 in length, and tho stigmas, taken by themselves, as 100 to 55. Nevertheless, this plant cannot be heterostyled. The anthers in the long-styled form are brown, tough, and fleshy, and less than half the length of those in the short-styled form, strictly as 44 to 100 ; and what is much more important, they were in a rudimentary condition in the two flowers examined by me, and did not contain a single grain of pollen. In the short-styled form, the divided stigma, which as we have seen is much shortened, is thicker and more fleshy than the stigma of the longstyled, and is covered with small irregular projections, formed of rather large cells. It had the appearance of having suffered from hypertrophy, and is probably incapable of fertilisation. If this be so the plant is dimcious, and judging from the two species previously described, it probably was once heterostyled, and has since been rendered dimcious by the pistil in the one form, and the stamens in the other having become functionless and reduced in size. It is, however, possible that the flowers may be in the same state as those of the common thyme and of several other Labiahe, in which females and hermaphrodites regularly co-exist. Fritz Muller, who thought that the present plant was heterostyled, as I did at first, informs me that he found bushes in several places growing quite isolated, and that these were completely sterile; whilst two plants growing close together were covered with fruit. This fact agrees better with the belief that the species is dioocious than that it consists of hermaphrodites and females; for if any one of the isolated plants had been an hermaphrodite, it would probably have produced some fruit. CHAP. III. MITCHELLA REPENS. 125 RuBIACE..tE. This great natural family contains a much larger number of heterostyled genera than any other one, as yet known. Mitchella repens.-Prof. Asa Gray sent me several living plants collected when out of flower, and nearly half of these proved long-sty led, and the other half short-styled. The white flowers, which are fragrant and which secrete plenty of nectar, always grow in pairs with their ovaries united, so that the two together produce "a berry-like double drupe."* In my first series of experiments (1864) I did not suppose that this curious arran gem en t of the flowers would have any influence on their fertility; and in several instances only one of the two flowers in a pair was fertilised ; and a large proportion or all of these failed to produce berries. In the ensuing year both flowers of each pair were invariably fertilised in the same manner; and the latter experiments alone serve to show the proportion of flowers which yield berries, when legitimately and illegitimately fertilised; but for calculating the average number of seeds per berry I have used those produced during both seasons. In the long-styled flowers the stigma projects just above the bearded throat of the corolla, and the anthers are seated some way down the tube. In the short-styled flowers these organs occupy reversed positions. In this latter form the fresh pollen-grains are a little larger and more opaque than those of the longstyled form. The results of my experiments are given in the following table. * A. Gray, 'Manual of the Bot. of the N. United States,' 1856, p. 172. |