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Show 122 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. In the long-styled forrn the stigmas project above the anthers, and the styles are nearly twice as long as those of the shortstyled form, in which the stigmas stand beneath the anthers. The stigmas in many, but not in all the short-styled flowers are larger than those in the long-styled. The anthers of the shortstyled flowers stand on a level with the stig1nas of the other form; but the stamens are longer by only one-fourth or one-fifth of their own length than those of the long-styled. Consequently the anthers of the latter do not stand on a level with, but rather above the stigmas of the other form. Differently from what occurs in the following closely allied genus, Sethia, the stamens are of nearly equal length in the flowers of the same form. The pollen-grains of the short-styled flowers, measured in their dry state, are a little larger than those frmn the long-styled flowers in about the ratio of 100 to 93. * , SETHIA ACUMINATA (ERYTHROXYLIDlE). Mr. Thwaites pointed out several years ago t that this plant exists under two forms, which he designated as forma stylosa et stamineu ; and the flowers sent to me by him are clearly heterostyled. In the long-styled form the pistil is nearly twice as long, and the stamens half as long as the corresponding organs in the short-styled form. The stigmas of the long-styled seem rather smaller than those of the short-styled. All the stamens in the short-styled flowers are of nearly equal length., whereas in long-styled they differ in length, being alternately a little longer and shorter; and this difference in the stamens of the two forms is probably related, as we shall hereafter see in the case of the short-styled flowers of Lythrum salicaria, to the 1nanner in which insects can best transport pollen from the long-styled flowers to the stigmas of the short-styled. The pollen-grains from the short-styled flowers, though variable in size, are to those of the long-styled, as far as I could make out, as 100 to 83 in their longer diameter. Sethia obtusifolia is heterostyled like S. acuminata. * F. M tiller remarks in his letter to me that the flowers, of which he carefully examined many specimens, are curiously vario.ble in the number of their parts : 5 sepals and petals, 10 stamens and 3 pistils are the prevailing numbers; but the sepals and petals often vary from 5 to 7 ; the stamens from 10 to 14, and the pistils from 3 to 4. t ' Enumeratio Plantarum Zeylanire,' 1864, p. 54. CHAP. III. .A3JGIPHILA ELATA. 123 CRATOXYLON FORMOSUM (HYPERIOINElE). Mr. Thiselton Dyer remarks that this tree, an inhabitant of Malacca and Borneo, appears to be heterostyled.* He sent me dried flowers, and the difl'erence between the two forms is conspicuous. In the long-styled form the pistils are in length to those of the short-styled as 100 to 40, with their globular stigmas about twice as thick. These stand just above the numerous anthers and a little beneath the tips of the petals. In the short-styled form the anthers project high above the pistils, the stigmas of which diverge between the three bun Ues of stamens, and stand only a little above the tips of the sepals. The stamens in this form are to those of the long-styled as 100 to 86 in length ; and therefore they do not differ so much in length as do the pistils. Ten pollen-grains from each form were measured, and those from the short-styled were to those from the long-styled as 100 to 86 in diameter. This plant, therefore, is in all .respects a well-characterised heterostyled species. lEGIPHILA ELATA (VERBENACElE). Mr. Bentham was so kind as to send me dried flowers of this species and of ..!E. mollis, both inhabitants of South America. The two forms differ conspicuously, as the deeply bifid stigma of the one, and the anthers of the other project far above the mouth of the corolla. In the long-sty led form of the present species, the style is twice and a half as long as that of the shortstyled. The divergent stigmas of the two forms do not differ much in length, nor as far as I could perceive in their papilloo. In the long-styled flowers the filaments adhere to the corolla close up to the anthers, which are enclosed some way down within the tube. In the short-styled flowers the filaments are free above the point where the anthers are seated in the other form, and they project from the corolla to an equal height with that of the stigmas in the long-styled flowers. It is often difficult to measure with accuracy pollen-grains, which have long been dried and then soaked in water ; but they here manifestly differed greatly in size. Those from the short-styled flowers were to those from the long-styled in diameter in * ' Journal of Botany,' London, 1872, p. 26. |