Journal Article

Floral Structure of <i>Kirkia</i> (Kirkiaceae) and its Position in Sapindales

Julien B. Bachelier and Peter K. Endress

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 102, issue 4, pages 539-550
Published in print October 2008 | ISSN: 0305-7364
Published online August 2008 | e-ISSN: 1095-8290 | DOI:
Floral Structure of Kirkia (Kirkiaceae) and its Position in Sapindales

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry


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Background and Aims

The monogeneric Kirkiaceae (Sapindales) were formerly placed as Kirkioideae in Simaroubaceae. However, recent molecular phylogenetic studies indicate that they are not in Simaroubaceae and they appear to be sister to the clade of Anacardiaceae plus Burseraceae. Such affinity was never considered or discussed since the first description of Kirkia. The present study is the first detailed analysis of the floral structure of a representative of Kirkiaceae and the first comparison with other sapindalean families, especially Anacardiaceae and Burseraceae.


Floral structure of Kirkia wilmsii was studied using transversal and longitudinal microtome section series, scanning electron microscopy and light microscopy.

Key Results

The flowers of Kirkia wilmsii are morphologically bisexual but functionally unisexual. They are polysymmetric, isomerous (tetramerous) and haplostemonous. The ovary is syncarpous and entirely synascidiate. The floral apex forms a hemispherical protrusion on top of the ovary. The styles are free but postgenitally united and apically form a stigmatic head with a compitum. Each carpel is uniovulate (biovulate in a few other species) and ovules are crassinucellar, bitegmic and slightly campylotropous. The micropyle is formed by both integuments and is unusually long. The unusual two radially disposed locules in each carpel in the former genus Pleiokirkia can be explained developmentally by the two offset and tightly contiguous lateral placentae.


Paralleling the molecular results, a suite of floral features supports the position of Kirkiaceae close to the Anacardiaceae–Burseraceae clade, and not in Simaroubaceae.

Keywords: Kirkiaceae; floral structure; gynoecium; Sapindales; Anacardiaceae; Burseraceae; monoecy; functional dioecy; heterodichogamy

Journal Article.  7755 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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