Flora of North America species comparison

In their extreme expression, the leaves of Atriplex argentea var. rydbergii are narrowly elliptic, tapering to both ends, but those extreme forms are connected through a graded series with oval-ovate ones, which tend to maintain the acute-cuneate base, however. The broad-leaved forms are intermediate to var. argentea. Tapering of leaf base to petiole is not restricted to this variety, however. Similar leaf shape occurs rather widely through the species as a whole, but in no place is it so consistently geographically correlated as in the Four Corners region.

H. C. Stutz and G. L. Chu (1997) compared their newly proposed Atriplex pachypoda from southwest Colorado and northwest New Mexico with the A. caput-medusae phase of what is considered herein as A. saccaria var. saccaria. Fruiting bracteole shape, marginal tooth arrangement, and compression are so strikingly similar to those of the A. argentea complex that the relationship with the latter group is apparent. Indeed, the closely contiguous var. rydbergii is nearly identical in all except subtle differences in bracteole shape and the disposition of staminate flowers in a terminal spike or panicle, which is apparently not an entirely constant feature. Arrangement of staminate flowers in terminal spikes appears at once to be a striking feature of var. rydbergii, but the spikes are evanescent, often lacking by fruiting time. And, there are some specimens of that variety in which the staminate flowers were evidently mainly, if not entirely, in axillary glomerules. Because of the similarities to var. rydbergii and the inconsistence of characteristics regarded by its authors as diagnostic, A. pachypoda is herein relegated to synonymy.

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

Genera ca. 100, species ca. 1500 (27 genera, 168 species in the flora).

A number of species introduced from Europe and Asia are weedy in North America. The widespread distribution of the family in the deserts of Eurasia and Australia is indicative of the ancient status of the family. Fossil pollen from this family dates to the Maestrichtian, providing the oldest known fossils in the Caryophylliidae.

Plants in this family typically have Crassulacean Acid Metabolism, have either a C3 or C4 photosynthetic pathway (W. V. Brown 1975; G. W. Welkie and M. Caldwell 1970), accumulate organic acids, free nitrates, and oxalates, and often contain alkaloids. Along with other members of the Caryophyllales, members of the family contain pigments called betalains (named for the genus Beta) rather than anthocyanins.

Economically important members of this family include spinach and chard (Spinacia oleracea) and beets (Beta vulgaris). Seeds in this family generally provide a rich source of protein, and one species, Chenopodium quinoa, is gaining widespread acceptance as a cereal crop. Toxicity from high levels of nitrates or oxalates has been reported for a number of species (J. M. Kingsbury 1964), and the pollen is known to be allergenic (T. C. Fuller and E. McClintock 1986). The nutritional characteristics of many species that we share with northern Asia were described by M. M. Iljin (1936).

Molecular and morphologic studies provide evidence supporting the inclusion of the Chenopodiaceae within Amaranthaceae (Angiosperm Phylogeny Group 1998; W. S. Judd and I. K. Ferguson 1999; J. E. Rodman 1990). However, until discordant elements within these lineages, such as Sarcobatus (H.-D. Behnke 1997), are interpreted within a larger evolutionary scheme, the disposition of family groups remains problematic.

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