Petalonyx

Petalonyx thurberi

Petalonyx is a plant genus of the family of flowers nettle plants ( Loasaceae ) and the only member of the subfamily of Petalonychoidae. It contains five species that are native to northern Mexico and the southwestern United States.

Description

Petalonyx are shrubs or subshrubs that grow mostly from a thickened, perennial rootstock, the bark often has thick layers of cork on. Nettle hair missing. The leaves are alternate and filled with short, branched bristles.

The inflorescences are terminal clusters. Before the upright, fivefold individual flowers are two bracts, the flowers grow achselbürtig of a supporting sheet.

The often nailed, white petals are to approach free and have a clearly visible midrib. The five stamens are episepal (ie before the sepals ), occasionally offset by the seemingly verwachsenkronblättrigen flower structure on the outside of the crown or at the always threadlike stamens enclosed by the edges of the petals.

The ovary has a hanging ovule. The fruit is a capsule irregularly pentagonal, which remains connected to the support sheet and the two continue reading, but the sepals are obsolete. The chromosome number is 2n = 46

Dissemination

The species are common in desert areas in northern Mexico and the southwestern United States.

System

The genus is clearly distinguished from other genera of the family due to the morphology of inflorescences, flowers and fruits, and is therefore classified in its own subfamily Petalonychoidae. The genus includes five species:

• Petalonyx crenatus A. Gray ex S.Watson
• Petalonyx linearis Greene
• Petalonyx nitidus S.Watson
• Petalonyx parryi A. Gray
• Petalonyx thurberi A. Gray

Was first described the species from Asa Gray, the description of the subfamily happened in the course of extensive systematic work on the family by Maximilian Weigend 1997 and 2006.

Evidence

• Maximilian Weigend: Loasaceae. In: Klaus Kubitzki (ed.): The Families and Genera of Vascular Plants. Volume 6: Flowering Plants, Dicotyledons: Celastrales, Oxalidales, Rosales, Cornales, Ericales. Springer, Berlin / Heidelberg / New York 2004, ISBN 3-540-06512-1, pp. 248, doi: 10.1007/978-3-662-07257-8 ( limited preview on Google Book Search ).
• Maximilian Weigend: Familial and generic classification, online, accessed July 19, 2008