Gillenia (syn. Porteranthus) is a genus of two species of perennial herbs in the Rosaceae family. Common names for plants in this genus include: Bowman's root, Indian-physic, American ipecac. This genus is endemic to dry open woods with acidic soils in eastern North America. Both plants are subshrubs with exposed semi-woody branches and serrated leaves; the larger lower leaves are divided into palmately arranged leaflets. Plants bloom in May, June, or July; blooms are composed of five slender white petals which are loosely arranged and typically appear slightly twisted and limp as if they were wilted. The flowers mature into small capsules. These plants are often planted as ornamentals and used medicinally as an herbal remedy.
Traditionally this genus is considered a member of subfamily Spiraeoideae, but it was moved to subfamily Maloideae, when it became apparent that it comes from the lineage which lead to the Maloideae (which arose from within the Spiraeoideae). More recently, subfamily Spiraeoideae has been expanded to include all of the Maloideae (as well as subfamily Prunoideae).
Gillenia has a haploid chromosome number of 9; the rest of the Maloideae have a haploid chromosome number of 17 (which was probably produced from a Gillenia-like ancestor by doubling the genome and then losing a chromosome). Flower structure and fossil evidence also point to Gillenia sharing distinctive features with the Maloideae. Another similarity between Gillenia and the rest of the Maloideae is susceptibility to Phragmidium fungus. Differences between Gillenia and most Maloideae include the chromosome number and the latter being solely woody pome bearing plants (Gillenia is herbaceous).
The name Porteranthus (Britton ex Small) has sometimes been used for this genus. The name Gillenia was thought to be already occupied by Gillena, a very similar name used by Michel Adanson as a synonym for Clethra (Under the International Code of Botanical Nomenclature "names that are so similar that they are likely to be confused" should be treated as homonyms Art. 53.3-5). However, a proposal to formally conserve Gillenia was mooted after it was determined that Gillena was not validly published and a vote decided that it and Gillenia were not likely to be confused. Thus, Gillenia is the correct name (and Porteranthus was validly published but is superfluous and illegitimate Art. 52.1).
The two similar species can be distinguished by their stipules. In G. stipulata, the stipules at the base of the leaves, which are round and deeply toothed, persist throughout the life of the plant. In G. trifoliata the long slender stipules are quickly deciduous, this species also tends to have longer leaves and petals.
* G. trifoliata or Porteranthus trifoliatus -- mountain Indian physic
The Flora of North America volume containing this genus is expected to be published in 2009.
1. ^ a b Potter, D., et al. (2007). Phylogeny and classification of Rosaceae. Plant Systematics and Evolution. 266(1–2): 5–43.
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