Morphological studies in Zygophyllaceae II. The floral development and vascular anatomy of Peganum harmala

Floral development and vascular anatomy are investigated in Peganum harmala, emphasizing its unusual androecium with 15 stamens. Sepals arise successively; petals emerge simultaneously with five antesepalous stamens. The five stamen pairs arise in the space between the petals and the antesepalous stamens. The gynoecium arises from three carpel primordia with evidence of two reduced carpels. Placentae are axile and each bears two double rows of ovules. A weakly developed nectary surrounds the base of the ovary. The antepetalous stamen traces diverge from a common supply to petals and sepal laterals, independent of the antesepalous stamen traces. The androecium of Peganum is described as a derived obdiplostemonous form, differing from the complex haplostemonous androecium of Nitraria. ''Congenital dedoublement'' cannot adequately explain the origin of the paired antepetalous stamens; two stamens can arise either by the splitting of a common primordium or independently, and both ways of inception are best understood as extremes of a gradation. The systematic position of Peganum is discussed in relation to other Zygophyllaceae using a cladistic analysis with Ptelea (Rutaceae) and Quassia (Simaroubaceae) as outgroups. The basal division in the Zygophyllaceae is between Peganum and the rest of the family.status: publishe

What is the taxonomic status of Polygonella? Evidence of floral morphology

A comparative morphological study of floral characters of the North American genus Polygonella and the four currently accepted sections of Polygonum s. str. (sect. Polygonum, sect. Duravia, sect. Pseudomollia, sect. Tephis) has been carried out with light microscopy (LM) and scanning electron microscopy (SEM). Flowers were investigated for macromorphological characters, tepal epidermal characters, pollen, and fruit morphology and anatomy. Results demonstrate that the limits between both genera become blurred through section Duravia of Polygonum, especially in characters of pollen and fruit morphology. Polygonum sect. Duravia and Polygonella share a wealth of intergrading floral and vegetative characters at the macroscopic, as well as ultrastructural, level (pollen morphology, fruit morphology, flower structure, vegetative anatomy). These characteristics, especially the pollen morphology, are sharply delimited from section Polygonum. Evidence presented here allows for a broader concept of Polygonum s. str. to be adopted, with an extended section Duravia including subsections Duravia and Polygonella. A cladistic analysis of morphological characters supports two distinct clades, section Polygonum with subsections Polygonum and Tephis, and section Duravia with subsections Duravia and Polygonella.status: publishe