Pollen morphology is widely used in taxonomic treatments of tribe Vernonieae, and differences in exine structure and aperture form have been described for many species within the genera comprising the tribe. However, in recent years a number of new species have been described and, in the present paper, we describe in detail the pollen of 24 species of the tribe which are either endemic or uncommon to certain regions of Argentina or of Paraguay. The pollen of these species are radially symmetrical and more or less spheroidal, 3-colporate or, in one species, 3-porate; the exine may be tectate or semitectate and microperforate, with echinate lophae or, in the 3-porate example, psilate lophae. Using a range of characteristics related to size, shape, wall thickness, apertures and tectum surface morphology, five of the six pollen types previously described for tribe Vernonieae, and a subtype, are recognized. Our results support the usefulness of pollen morphology in helping to determine the taxonomic position of species within tribe Vernonieae.

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The pollen of Cliococca selaginoides (Lam.) C. M. Rogers & Mildner and eight Linum L. species from Argentina were examined using light and scanning electron microscopy. Both genera share pollen grains which are 3zonocolpate, isopolar, radiosymmetric, spheroidal and medium to large in size. The sculptural elements of the exine are gemmae or clavae, which allow the genera to be distinguished and the species to be characterised. In Cliococca Bad., the pollen is exclusively gemmate whereas in Linum the pollen is gemmate and clavate (except in L. catharticum L. whose pollen has only gemmae which are apically microechinate). The statistical analyses of quantitative and qualitative morphological characteristics were performed. A key to identify and distinguish the pollen types and subtypes is also provided. A generalized procrustes analysis (GPA) of joint characterisation based on both qualitative and quantitative characters identified four distinct groups.

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<div><p class="MsoNormal"><span style="font-family: Arial; color: #231f20;">&nbsp;</span><span style="font-family: Verdana;">En este trabajo se estudia la morfolog&iacute;a del polen de 93 especies, pertenecientes a 19 g&eacute;neros, en su mayor&iacute;a americanos, de la tribu <em style="mso-bidi-font-style: normal;">Hedysareae</em> (Leguminosae) y de 3 especies de Adesmia (Adesmieae).</span></p><p class="MsoNormal" style="background: white;"><span style="font-family: Verdana;">En base a este estudio se establecen relaciones palinol&oacute;gicas entre los distintos g&eacute;neros. En este sentido los caracteres de mayor valor taxon&oacute;mico son: tipo de abertura y de ornamentaci&oacute;n. De acuerdo a ellos se agrupan los g&eacute;neros en 3 grupos bien definidos:</span></p> <p class="MsoNormal" style="background: white;"><span style="font-family: Verdana; color: black;">&nbsp;</span><span style="font-family: Verdana;">- granos colpados y, semitectados: <em style="mso-bidi-font-style: normal;">Stylosanthes, Arachis, Zornia, Pachecoa </em>y<em style="mso-bidi-font-style: normal;"> Chapmannia</em>;</span></p> <p class="MsoNormal" style="background: white;"><span style="font-family: Verdana; color: black;">- granos colporados y semitectados: <em style="mso-bidi-font-style: normal;">Aeschynomene, Chaetocalyx, Lespedeza </em>y<em style="mso-bidi-font-style: normal;"> Poiretia</em>;</span></p> <p class="MsoNormal" style="background: white;"><span style="font-family: Verdana; color: black;">- granos colporados y tectados: <em style="mso-bidi-font-style: normal;">Nissolia, Bergeronia, Desmodium, Coronilla </em>y<em style="mso-bidi-font-style: normal;"> Ornithopus</em>.</span></p> <p class="MsoNormal" style="background: white;"><span style="font-family: Verdana; color: black;">En este &uacute;ltimo grupo, la ornamentaci&oacute;n del tectum es caracter&iacute;stica de cada g&eacute;nero, lo que permite identificarlos.</span></p> <p class="MsoNormal" style="background: white;"><span style="font-family: Verdana; color: black;">Adem&aacute;s, en base a los datos aportados por el polen, se eval&uacute;a la posici&oacute;n taxon&oacute;mica de los g&eacute;neros <em style="mso-bidi-font-style: normal;">Zornia, Lespedeza </em>y<em style="mso-bidi-font-style: normal;"> Discolobium</em>.</span></p></div>