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.)

This species forms hybrids with Atriplex confertifolia and A. gardneri varieties (see var. bonnevillensis). Materials from the vicinity of the type locality of the species in South Dakota are low subherbaceous plants that differ from our shrubby tall material. However, the type area is presently covered with water from a dam on the Missouri River, and it is not possible to exclude the possibility of A. canescens as it has been interpreted for the past century to have existed at that site during the Lewis and Clark Expedition, if that is indeed where the lectotype was collected.

Varieties 4 (4 in the flora).

Nuttall’s new combination Atriplex canescens was based on Calligonum canescens Pursh. Watson based his new name A. nuttallii directly on A. canescens Nuttall, i.e., including the citation of Nuttall’s “Genera, 1. 197,” and on its basionym, C. canescens. The name A. nuttallii is thus a nomenclatural synonym of A. canescens and was thus illegitimate at its inception. It cannot be resurrected by even the most sophisticated arguments. A sheet of Atriplex canescens, noted as “a shrub,” taken by Nuttall on the 1810 Missouri River expedition is extant in the Lambert herbarium (PH). It bears several, obviously shrubby, staminate flowering branches, but the only pistillate branch is very immature. The name A. gardneri, also cited provisionally by Watson within the concept of A. nuttallii, clearly has priority over other names for that widely distributed species complex. Attempts at leptotypification of the name nuttallii by J. McNeill et al. (1983) and H. C. Stutz and S. C. Sanderson (1998) are both superfluous, the name being illegitimate.

C. A. Hanson (1962) noted the similarity between the occasional wingless fruiting bracteoles of Atriplex canescens and A. gardneri var. falcata. He noted further that the bracts of both species lack lateral teeth subtending the terminal ones, have terminal teeth united half their length, and have indurate bracts. Whether such similarity indicates relationship or mere coincidence is open to question. However, A. canescens is known to form hybrids with most, if not all, portions of the gardneri complex and with other woody species whose range it overlaps as well.

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