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Sauvagesia erecta L. is a small pantropical herb in the family Ochnaceae. Flowers are unusual in that in addition to petals there is an inner whorl of five petaloid structures and clusters of small spathulate appendages situated between the petals and petaloid structures. The petaloid structures overlap to form a cone enclosing the androecium and gynoecium. Both the spathulate appendages and petaloid structures have traditionally been considered to be staminodial in origin. The floral development and floral anatomy of S. erecta was investigated using scanning electron microscopy and light microscopy. Our analysis shows the late initiation of antepetalous petaloid structures following petals, gynoecium, and antesepalous stamens. This is consistent with the phyllotactic and developmental sequence for a second whorl of stamens. Further to this the vascular traces feeding both the petaloid structures and the stamens split from a common trace low in the receptacle of the flower. These observations confirm the staminodial nature of these petaloid structures. The primordia for the spathulate appendages arise very late in the ontogeny of the flower after all other organs have initiated and are already well developed. The receptacle between the petals and petaloid staminodes expands into a narrow androgynophore and the initial spathulate appendages arise in an antesepalous position below the stamens and staminodes. Further primordia develop around the first-formed appendages in centrifugal sequence, eventually joining neighbouring appendages in a continuous girdle. The vascular traces associated with the appendages are randomly attached to the staminal traces and divide repeatedly before connecting to individual structures. The nature of a corona is discussed and it is concluded that the generally used definition is not adequately reflecting the homology of structures described as a corona. Our findings strongly suggest that the appendages are novel organs and could be considered as equating to the corona structures seen for example in Passifloraceae, Velloziaceae or Amaryllidaceae. Therefore the appendages are best interpreted as hypanthial emergences and not as staminodes. Comparison with other Ochnaceae suggests that outer filamentous staminodes found in several genera are best interpreted as a corona, in contrast to inner antepetalous staminodes. However, the function of the appendages in plant-insect interactions is unclear, except for attraction. Flowers of Sauvagesia are buzz-pollinated and the cone-like petaloid staminodes would appear to have a dual function in protecting the reproductive organs from damage and in directing the pollen released onto visitors. [ABSTRACT FROM AUTHOR]

The pollen of 30 taxa (27 species, one subspecies and two varieties) in two genera, viz Polygonum s. str. and Polygonella was investigated with LM and SEM, and some selected taxa with TEM. In all genera investigated the pollen is prolate to spheroidal, and the aperture is mostly tricolporate, rarely panto-hexacolporate (especially Polygonum section Polygonum). The exine sculpturing pattern is the most variable feature. Three types of exine can be recognized. Type 1 ( Avicularia-Type, sensu Hedberg) - All species of section Polygonum and section Tephis share the smooth tectate exine with spinules, sometimes the surface is more or less rough ( Polygonum afromontanum in section Tephis). Type 2 ( Pseudomollia-Type, sensu Hong) - Pollen of Polygonum molliaeforme (section Pseudomollia) has the exine, which is verrucose on both poles and nearby the mesocolpium, and mostly psilate around the ectoaperture. Type 3 ( Duravia-Type, sensu Hedberg) - Pollen grains of Polygonum section Duravia and Polygonella have the exine which is semitectate-reticulate at the mesocolpium and the poles, and rugulate/reticulate or sometimes foveolate with microspinules around the ectoapertures. The pollen grains in four taxa (viz Polygonum section Pseudomollia, P. section Duravia and genus Polygonella) have a well-marked dimorphism of the ektexine, which is considered to be a synapomorphic condition. The differences of pollen grain between the genus Polygonella and Polygonum section Duravia are almost non existent and clearly interrelated. It is therefore postulated that the similarity in pollen of both taxa is not the result of convergency, but is interpreted as a homology. It is noteworthy that the pollen of Polygonum molliaeforme (section Pseudomollia) appears as intermediate between the Avicularia-type and the Duravia-type, and is well supported the value of separated section for its own. Additionally, in TEM, some exine ultrastructures (e.g. columellae, foot layer, endexine) appear to be valuable characters for comparison between/among taxa. The systematic potentialities of the pollen data of the studied taxa at various systematic levels are also discussed. [ABSTRACT FROM AUTHOR]

The floral development and anatomy ofDirachmahas been investigated with SEM and LM to discuss the relationship of Dirachmaceae with putative sister taxa (e.g. Rhamnaceae, Malvaceae, Barbeyaceae, Elaeagnaceae) on the basis of morphological synapomorphies. Flowers are initiated in axillary position on terminal branches. An epicalyx consisting of six to eight bracteoles surrounds the valvate calyx. Petal initiation is strongly retarded and primordia arise independently opposite the stamen primordia. The carpels arise independently and become weakly fused at the base; a single ovule develops in an axile position. A hypanthium develops by interprimordial growth between petals and stamens. Nectaries arise in a pouch and are covered with trichomes positioned on a protuberance at the base of the petal. It is suggested that the solitary flowers are derived from compound cymose inflorescences. Comparison betweenDirachmaand species of Rhamnaceae demonstrates striking similarities in floral structure and anatomy. However, several characters are unique toDirachmaand support a family Dirachmaceae separate from Rhamnaceae. [ABSTRACT FROM AUTHOR]