630 stand ley: new genus of allioniaceae 



Mexico, which extended from 1849 to 1852. Two species were 

 described, S. diffusus and S. chenopodioides. There is no indi- 

 cation that the genus was based primarily upon either species; 

 consequently the first, S. diffusus, may be taken as the type. 



Selinocarpus is related to the large genus Boerhaavia, being dis- 

 tinguished chiefly by the broad, thin wings of the fruit. In the 

 latter, it is true, the fruit is sometimes winged, but the wings 

 are narrow, thick, and usually veined. No one, apparently, has 

 questioned the claims of Selinocarpus to generic rank, for the 

 plants are decidedly different in their general aspect from the 

 group of species comprised in Boerhaavia, as restricted by the 

 present writer. 4 



Since 1853 five species of Selinocarpus have been published, 

 the genus now being known to range from Nevada and southern 

 Utah to western Texas and southward to Coahuila, Mexico. 

 Upon close inspection of the seven species it is evident that one 

 of the two original ones, S. chenopodioides, differs in certain 

 floral characters from the genotype and the five subsequent addi- 

 tions to the genus. Its perianth is campanulate and conspicu- 

 ously constricted above the ovary, while in S. diffusus and the 

 other species the perianth is tubular-funnelform and not at all 

 constricted. In the case of the latter group of species the 

 perianth varies markedly, however, in shape and size, being 

 only 1 cm. long and with a short tube in S. angustifolius Torr., 

 and 2.5 to 4.5 cm. long, with a slender, elongate tube, in the other 

 species. In S. chenopodioides the perianth is 4 to 5 mm. long. 

 In the last, moreover, the stamens are 2 or rarely 3, their fila- 

 ments free from the perianth, while in S. diffusus and its allies 

 the stamens are 5 or 6, their filaments adherent to the perianth 

 tube. These striking differences in the perianth and androecium 

 are accompanied by habital differences, also : In S. chenopodioides 

 the flowers are aggregated in many-flowered, umbelliform cymes, 



(Allionia nyctaginea Michx.) the statement is made that it signifies "like Nycta- 

 ginia, a genus of this family." As a matter of fact, Michaux's species was pub- 

 lished many years before the generic name Nyctajinia. His specific name doubt- 

 less alludes to the resemblance of the leaves of the Allionia to those of the com- 

 mon four-o'clock, Mirabilis jalapa, the Nyctajo of pre-Linnaean botanists. 

 4 Contr. U. S. Nat. Herb., 12: 372-387. 1909. 



