Sandwort [Greek eremo-, solitary or deserted, and gone, seed or offspring, allusion uncertain]

Ronald L. Hartman, Richard K. Rabeler, Frederick H. Utech

Plants perennial, often densely matted, usually with branched, woody base. Taproots slender or usually stout; rhizomes absent. Stems prostrate (nonflowering stems) or ascending to erect (flowering stems), simple or branched, terete. Leaves usually congested at or near base of flowering stems, usually connate, mostly sessile; blade 1-veined, needlelike or filiform to subulate or narrowly linear, succulent or not, apex blunt to usually apiculate or spinose. Inflorescences terminal, open to congested or umbellate cymes or sometimes flowers solitary; bracts paired (or clustered at summit of peduncle in some E. congesta varieties), reduced, foliaceous or scarious. Pedicels erect or flowers sessile. Flowers: perianth and androecium weakly perigynous; hypanthium shallowly cup-shaped; sepals 5, distinct or barely connate proximally, green (sometimes purplish in E. capillaris and E. eastwoodiae), linear-lanceolate to ovate, 1.8-12 mm, margins white, scarious, apex obtuse or rounded to acute, acuminate, or spinose, not hooded; petals 5, white, yellowish white, or occasionally pink or brownish, clawed or not, blade apex entire, erose, emarginate, or rarely 2-fid; nectaries usually 5, prominent at (or adjacent to in E. eastwoodiae) base of filaments opposite sepals, rarely absent; stamens 10, arising from hypanthium; filaments distinct; staminodes absent; styles 3, filiform, 2.5-3 mm, glabrous proximally; stigmas 3, subcapitate, smooth to papillate (50×). Capsules ovoid to urceolate, opening by 6 ascending to recurved teeth; carpophore present or usually absent. Seeds 1-10, dark reddish or greenish brown, tan, blackish purple, black, or gray, ovoid to pyriform or suborbicular, laterally compressed, smooth, rugulose, or tuberculate, marginal wing absent, appendage absent. x = 11.

Species ca. 89 (14 in the flora): north-temperate regions, esp. w North America, Eurasian mountains, Asia Minor.

Much of this treatment follows those by B. Maguire (1947, 1951) and M. F. Baad (1969) of Arenaria sect. Eremogone. The Eremogone “group” is morphologically distinctive (cespitose or matted, woody perennials with filiform to subulate leaves, stiffly erect to ascending flowering stems, and open to congested or umbellate cymes) and nearly all of the published chromosome counts are based on x = 11 (see also Baad), an uncommon base number in Arenaria in the narrow sense. The decision to recognize Eremogone, as used in W. A. Weber and R. C. Wittmann (1992) and R. D. Dorn (2001), is based largely on results of the molecular study of subfamily Alsinoideae by M. Nepokroeff et al. (2001). In that study, Arenaria (excluding Minuartia and Moehringia) was shown to be polyphyletic, with two distinct clades. One of the clades consists of seven species: five from Arenaria subg. Eremogone and two from the closely related subg. Eremogoneastrum; therefore the Eremogone group, as delimited by Maguire, is monophyletic.

While Eremogone is a distinct genus, there is considerable morphological variability among the species, with many, often geographically isolated, morphological types; see J. C. Hickman (1971) for a commentary on the situation, numerous examples of intermediate forms, and notes on their possible evolution. With this in mind, we have chosen not to adopt an infrageneric classification; J. McNeill's (1962) outline of Arenaria suggests that three species groups could be recognized within Eremogone.

Because of the aforementioned variability and intermediacy within and between taxa, the production of a satisfactory key has been a challenge and, as with those by B. Maguire (1947, 1951), likely will prove inadequate for at least a low percentage of specimens.

Reports of winged seeds in Eremogone possibly are derived from examination of immature material. The tubercles along the abaxial edge that have not yet expanded can appear as a lighter-colored band around a portion of the seed.

The morphology of the nectaries in Eremogone is very diverse, both among species and, in one case, among infraspecific taxa (E. macradenia). We feel that a morphogenetic study using scanning electron microscopy similar to the investigation of nectaries in Schiedea by W. L. Wagner and E. M. Harris (2000) may shed light on relationships within Eremogone.

Some suggestions for the identification of taxa of Eremogone follow.

In determining the shape of the sepals, several flowers should be evaluated and the membranous margins must be included, not just the central herbaceous portion. As this genus is in many ways a “problematic group,” some effort beyond what may be considered “normal” may be needed for accurate identification. This is because of the frequent need to observe floral details at high magnification (20 or 30×), preferably with a dissecting microscope. Furthermore, on dried specimens, a flower or two may need to be “boiled up” or otherwise rehydrated so that good, clear observations can be made. This is a practice that too often is avoided, to the detriment of accurate observation and identification, and should be standard in the study of pressed material.

SELECTED REFERENCES

Baad, M. F. 1969. Biosystematic Studies of the North American Species of Arenaria, Subgenus Eremogone (Caryophyllaceae). Ph.D. dissertation. University of Washington. Hickman, J. C. 1971. Arenaria, section Eremogone (Caryophyllaceae) in the Pacific Northwest: A key and discussion. Madroño 21: 201-207. Ikonnikov, S. S. 1973. Zametki o gvozdichnykh (Caryophyllaceae). I. O rode Eremogone Fenzl. Novosti Sist. Vyssh. Rast. 10: 136-142. Maguire, B. 1947. Studies in the Caryophyllaceae. III. A synopsis of the North American species of Arenaria sect. Eremogone Fenzl. Bull. Torrey Bot. Club 74: 38-56.