236 GENUS ATRIPLEX. 



species of Atriplex and A. canescens. Pterochiton was recognized by Nuttall (Jour. 

 Acad. Phila. II, 1:184, 1848), but otherwise it has been considered as not more than 

 a section or subgenus of Atriplex. 



Endolepis was proposed by Torrey (in Gray, Pacif. R. R. Rep. 12^47, 1860) on the 

 basis of a peculiarly shaped perianth in the staminate flowers and the presence of a 

 calyx in the pistillate flowers. But a calyx is sometimes present even in the type species 

 of Atriplex (A. hortensis). It will be demonstrated under A. phyllostegia (p. 267) that this 

 structure is vestigial and that in at least one species it may be found in all stages of sup- 

 pression. Therefore, its presence or absence can not be used for the separation of genera. 

 Endolepis was merged into Atriplex by Watson in his revision of the family above referred 

 to. Recently it has been revived as a genus by Rydberg (Bull. Torr. Club 30:248, 

 1903) and by Standley (N. Am. Fl. 21:72, 1916), while Macbride (Contr. Gray Herb, 

 n. s. 53:11, 1918) insists that it should not be given generic standing. 



Additional segregate genera have been proposed by European botanists, but they 

 include no American species. 



None of the above-mentioned proposals are maintained in the present paper. Instead, 

 they are all referred to the genus Atriplex, which, notwithstanding their inclusion, 

 remains a natural and easily defined group. But in order to maintain this unity it is 

 necessary to exclude one segregate formerly referred to Atriplex. This is the genus 

 Suckleya Gray (Proc. Am. Acad. 11:103, 1876), based upon Obione suckleyana Torrey. 

 This is a nearly prostrate annual herb with a habit unlike that of any true Atriplex. 

 Its generic standing is maintained on its peculiar fruiting bracts, which are strongly 

 obcompressed, i. e., flattened in a plane contrary to that of the original position of the 

 faces. The resulting fruit is winged dorsally, but these wings are not homologous with 

 the four prominent wings of Pterochiton. Suckleya has been accepted as a genus by 

 Bentham and Hooker, by Volkens, and by all of the more recent workers on the group. 



The American species of Atriplex have received monographic treatment by but three 

 authors. The first of these was Moquin-Tandon, who published his Chenopodearum 

 monographica enumeratio in Paris in 1840. This was followed, in 1849, by a monograph 

 by the same author in De Candolle's Prodromus (vol. 13, part 2, pp. 90 to 115) where 98 

 species of Atriplex and Obione are described, this number comprising all of the species 

 of the world known at that time. As indicated above, the genera just mentioned now 

 constitute the two subgenera of the genus Atriplex. The enormous amount of labor 

 involved in bringing together the scattered facts regarding the genus at that early date, 

 and the masterly way in which the species were organized and described, places all 

 later workers under deep obligation to this early specialist. 



No account covering the entire genus has appeared since the work of Moquin-Tandon. 

 The North American species, however, were given a new treatment in 1874 by Watson 

 in his Revision of the North American Chenopodiaceae (Proc. Am. Acad. 9:82-126, 

 1874). Here Obione is definitely reduced to Atriplex, which is then divided into three 

 sections, the first comprising annuals with the radicle inferior or subascending, the 

 second annuals with the radicle usually superior, and the third perennials with the 

 radicle usually superior. This treatment by Watson, which includes a key to the 40 

 accepted species, but in which only the new species are described, has served as a basis 

 for all accounts given in regional. State, and local floras up to 1916. In this year there 

 appeared an account of the North American Chenopodiales by Standley (N. Am. 

 Fl. 21:1-93). Standley follows Watson in the reduction of Obione to Atriplex, but 

 restores Endolepis as a distinct genus, to which 3 species are referred. His account of 

 Atriplex includes 103 species grouped into 29 sections. The comparatively large number 

 of species recognized is due in part to the adoption of a narrow species-concept; in part 

 to the dependence, as it seems to the present authors, upon certain characters since 



