Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The amount of information concerning the water-hyacinth grew in an explosive way during recent years due to its potential damaging or benefic effect on the environment, nevertheless the study of the population ecology of this plant has been neglected till now. In particular, the behavior of clonal populations in natural conditions. As a contribution to the understanding of the factors that regulate the structure of populations of Eichhomia crassipes in relation with its modular organization, we describe here the growth dynamics of the plants in two selected water bodies of Mexico. In contrast with the fast growth shown by populations living in euthrophicated environments, the production of growth units (ramets) by the plants is strongly limitated by an ecologicaly diverse environment but the phenotipic plasticity increases mainly in the vegetative and reproductive behavior.

A review of the taxonomic history of Nymphaea ampla (Salisb.) DC. is presented, since its description by Salisbury in 1805 up to the present, including the mention of various names which have been incorrectly referred to this taxon as synonyms, most notably Nymphaea gracilis Zucc. N. gracilis is easily distinguished from N. ampla, the only other Mexican species with which it might be confused, by several-morphological and field characters, namely: the margin of the leaf, shape of the rhizome, venation of the lower leaf surface, angle of aperture of the sepals, and altitudinal distribution . The results of this research lead us to the conclusion that N. ampla var. speciose (Mart. & Zucc.) Casp . is restricted at present to the Antilles and South America. The confusion created by Conard's work (1905) widening the range of this variety to temperate Mexico, by the inclusion of N. gracilis and N. undulata under this variety, has been clarified. Comparison of descriptions and type specimens of various Nymphaeas, which were involved in the problem, such as N. gracilis Zucc., N. flavo-virens Lehm. , N. undulate Lehm. , and N. tussilagifolia Lehm., indicates that all of them belong to the same species. Applying the rule of priority, the correct name which should be used for this plant is N. gracilis Zucc.

This work studies 17 species of mexican Araliaceae from the palynological point of view belonging to the genera Aralia, Dendropanax, Didymopanax, Redera, Oreopanax y Sciadodendron . All the pollen descriptions are presented at the generic level. The grains were studied based in scanning electron microscope and light microscope. It includes a dichotomous key for the genera grains. The results showed few differences between the pollen grains of the genera although some exine characters are important. Redera and Didymopanax presented an exine semi-tectate and the rest of the genera had tectate-perforate grains. This paper compared also some pollen characters with morphological ones, finding pollen characters considered primitive correlated with characters of primitive Araliaceae groups .

Four new species and one variety of Acourtia are described from Mexico: A. bravohollisiana, seemingly related to A. erioloma (Blake) Reveal & King and to A. scapiformis (Bacigalupi) Turner; A. discolor, perhaps akin to A. erioloma (Blake) Reveal & King; A. fragrans, similar to A. tlzurberz (Gray) Reveal & King and to A. oxylepis (Gray) Reveal & King; A. huajuapana var . actinomorpha, characterized by its regular flowers; and A. matudae, perhaps derived from A. lzebeclada DC.

New from Mexican aquatic plants

Baccharis erosoricola and Astranthium reichei are described as new on the basis of specimens collected in the state of Mexico . B. erosoricola seems to be closely related to B. pteronioides DC., while A. reichei shows similarities to A. xylopodum Larsen.

New taxa and new records for México in Violaceae and Scrophulariaceae are presented , based on collections from the Zona de Uxpanapa, Veracruz-Oaxaca. Rinorea uxpanapana (Violaceae) is described as new, and R. deflexiflora is reported for the first time from México. In Scrophulariaceae, Uroskinnera hirtiflora var. breviloba is a new variety, and the asiatic weed Lindernia antipoda is new to México.

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