Flora of North America species comparison

Problems with prior applications of the name Atriplex mucronata lie in the mistaken determination of the place of publication as Amer. Monthly Mag. & Crit. Rev. 2: 176. 1818 (where the name is only mentioned), instead of 2: 119. 1817 (where accompanied by a description and notes). H. M. Hall and F. E. Clements (1923) evidently relied on P. C. Standley’s (1916) interpretation, which indicated the wrong citation (see also A. dioica Rafinesque as an identical example). Hall and Clements applied the name mucronata to their interpretation of A. patula subsp. hastata or to A. hastata (i.e., to A. prostrata according to this treatment).

The treatment of Obione by C. H. B. A. Moquin-Tandon (1849) included “A. mucronata Rafin.!” as a synonym of O. arenaria. Possibly a sheet in the Prodromus herbarium at Geneva was the basis for that decision. It has two mounted specimens, one labeled A. arenaria Nuttall, collected by Nuttall in “N. Jersey, 1826,” and a second labeled “Atriplex mucronata Rafinesque (A. arenaria Nuttall, N. Jersey) Maritime NY, Rafinesque 1819.” From that information (although the year is 1819, not 1817), and from the description of the taxon, it seems clear that A. arenaria Nuttall is a later synonym of A. mucronata Rafinesque by at least half a year.

H. A. Gleason and A. Cronquist (1991) indicated that this taxon, by whatever name, is “perhaps better treated as a variety of the more tropical Atriplex pentandra (Jacquin) Standley, but the proper nomenclatural combination not yet made.” The present writer agrees with that conclusion, but such subjugation might indicate further contraction into the species of additional closely related taxa, e.g., A. wrightii, which is clearly closely allied as well.

Plants from the coastal states from New England south to New Jersey are much alike and seldom, if ever, display prominent, terminal, naked spikes or panicles with beadlike glomerules of staminate flowers. Plants from Florida westward sometimes have such staminate spikes or panicles.

Specimens from Florida and some from Texas can be distinguished from Atriplex pentandra only with difficulty, especially those individuals with entire leaves. However, the fruiting bracteole length-width ratio and overall shape, with some allowance for overlap, can serve to distinguish most specimens; those of A. mucronata are proportionately longer than broad and, on average, larger.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Endolepis covillei was treated within the synonymy of Atriplex phyllostegia (Torrey) S. Watson by H. M. Hall and F. E. Clements (1923).

H. C. Stutz et al. (1993) placed Atriplex covillei within Endolepis, based in large part on the presence of a perianth subtending the pistil within the fruiting bracteoles and on the lack of Kranz anatomy in the leaves. The pattern of venation is, nevertheless, very similar to that in species with Kranz anatomy. The presence of perianth scales in the pistillate flowers of A. covillei has been regarded as evidence of relationship with A. suckleyi. Despite placement of these taxa within Endolepis by Stutz et al. Atriplex covillei is possibly more closely allied to the morphologically similar and partially sympatric A. phyllostegia than it is to strongly dissimilar and the distantly disjunct A. suckleyi. Stutz and his associates placed great emphasis on the presence of reduced perianth segments subtending the pistil within the fruiting bracteoles of A. covillei. Calyces per se, otherwise known only in A. suckleyi and A. pleiantha, probably have arisen independently. Their presence does not necessarily indicate a close relationship. Stutz et al. pointed to other differences aside from the calyx of the pistillate flowers, and it is apparent that the two entities can stand as distinct species. To segregate A. covillei within a separate genus and to ally it with a species to which its relationships are obscure at best, stretches logic beyond reason.

(Discussion copyrighted by Flora of North America; reprinted with permission.)