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The embryological characters of <i>Megacodon stylophorus</i> (C. B. Clark) H. Smith and <i>Veratrilla baillonii</i> Franch. are described for the first time and the systematic relationships of <i>Megacodon</i> and <i>Veratrilla</i> are discussed. Both species share the following embryological features. The anthers are tetrasporangiate. The formation of anther walls is of the Dicotyledonous Type. The tapetum is of glandular type with uninucleate cells which have a dual origin. The tapetal cells on the connective side show radial elongation or periclinal division and intrude into the anther locule to form ‘placentoids’. Cytokinesis in the microsporocyte meiosis is of the simultaneous type and the microspore tetrads are nearly always tetrahedral, rarely decussate. The ovary is bicarpellate and unilocular. The ovule is unitegmic and tenuinucellar. The formation of the embryo sac is of the Polygonum Type. Before fertilization, the two polar nuclei fuse into a secondary nucleus. Fertilization is porogamous. The development of the endosperm is of the Nuclear Type. However, the two species show variation in the following features: the number of cell layers which form the anther locule wall; construction of the wall of the mature anther; cell number in mature pollen grains; ovule number in cross sections of placentae; degree of ovule curvature; character of the hypostase and seed shape. In a comparison with the other taxa in the tribe Gentianeae using embryological features, <i>Megacodon</i> is referred to as an independent genus and should be treated as a member of the subtribe Swertiinae; <i>Veratrilla</i> is better separated from <i>Swertia s</i>.<i>l</i>. as an independent genus. <i>Veratrilla</i> is more derived than <i>Swertia s</i>.<i>s.</i> and shows a close relationship with <i>S. tetraptera</i>. © 2005 The Linnean Society of London, <i>Botanical Journal of the Linnean Society</i>, 2005, <b>147</b>, 317-331.
The embryological features of three species of <i>Swertia</i> (<i>s.l.)</i>-<i>S. erythrosticta</i>, <i>S. franchetiana</i>, and <i>S. tetraptera</i>- were characterized, and the observations were used, together with previously gathered data on other species, to evaluate a recently proposed polyphyly, based on molecular data, of <i>Swertia s.l.</i> Comparisons of species within the genus showed that they have diversified embryologically, and there are significant between-species differences. Notable features that vary between species include the number of cell layers that form the anther locule wall, the construction of the wall of the mature anther, tapetum origin, the cell number in mature pollen grains, the structure of the fused margins of the two carpels, the ovule numbers in placental cross-sections, the shape of the mature embryo sac, the degree of ovule curvature, antipodal variation and the presence of a hypostase, and seed appendages. They share characters that are widely distributed in the tribe Gentianeae, such as a dicotyledonous type of anther wall formation, a glandular tapetum with uninucleate cells, simultaneous cytokinesis following the meiosis of the microsporocytes, tetrahedral microspore tetrads, superior, bicarpellary and unilocular ovaries, unitegmic and tenuinucellar ovules, <i>Polygonum</i>-type megagametophytes, progamous fertilization, nuclear endosperm, and Solanad-type embryogeny. The presence of variation in embryological characters amongst the species of <i>Swertia s.l.</i> strongly supports the view that <i>Swertia s.l.</i> is not a monophyletic group. <i>Frasera</i> is better separated from <i>Swertia s.l.</i> as an independent genus, and is only distantly related to <i>Swertia s.s.</i> judging from the numerous differences in embryology. <i>Swertia tetraptera</i> is very closely related to <i>Halenia</i>, as they show identical embryology. © 2007 The Linnean Society of London, <i>Botanical Journal of the Linnean Society</i>, 2007, <b>155</b>, 383-400.