Biebersteinia, a perennial herb of five species distributed from Greece to Central Asia, was long considered to be placed in, or near Geraniaceae. Recent molecular analyses, however, have shown that the genus is the sole member of the family Biebersteiniaceae in Sapindales (not including Geraniaceae). Here, we report the embryological features of Biebersteinia and provide embryological corroboration for the molecular sapindalean affinities of the genus. We compared its embryology with those of eight other families of Sapindales, as well as with those of the related orders Huerteales, Malvales, and Brassicales. Overall comparisons showed that Biebersteinia fits in Sapindales because of the presence of anther tapetal cells with polyploid nuclear mass and non-fibrous exotegmen. Further, the genus is characterized by three-celled pollen grains, tetrasporic 16-nucleate Penaea-type female gametophyte, unitegmic ovules, pseudoporogamy, and the chalaza shifting its position near the concave side in the post-fertilization stage. A considerable number of autapomorphies, combined with the lack of synapomorphies with other sapindalean families, supports placing Biebersteinia in its own family. Biebersteiniaceae appear to represent an early divergent lineage of Sapindales. Previous descriptions of seed coats, which were considered to have developed from "bitegmic" ovules, were revised.
Harrisonia, a genus of three or more species distributed from tropical Africa and Southeast Asia to northern Australia, has long been considered a member of Simaroubaceae. Recent molecular analyses, however, have shown that the genus is assigned to subfamily Cneoroideae of Rutaceae, in which Cneoroideae (eight genera) are sister to the remainder of the family (‘core Rutaceae’). Here, we report embryological features of Harrisonia based on published and newly obtained data and provide morphological corroboration for the molecular affinities of the genus and Cneoroideae. We compared its embryological features with those of seven other genera of Cneoroideae and with those of the core Rutaceae and related families (Meliaceae, Simaroubaceae and Sapindaceae). Comparisons showed that Harrisonia fits within Cneoroideae through possessing campylotropous seeds with a multi‐cell‐layered endotesta. Embryological evidence, like molecular evidence, further shows that, in Cneoroideae, Harrisonia probably has affinities to a group of Bottegoa, Cedrelopsis, Cneorum and Ptaeroxylon by sharing a micropyle formed by the inner integument alone and solitary oil cells in the testa. Except for Harrisonia, Cneoroideae are still poorly understood embryologically and further investigations are needed.
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