Corispermum
bug-seed, tick-seed
erect or ascending, rarely prostrate, branched (rarely simple), not jointed, not armed, not fleshy.
alternate, sessile;
blade [obovate-elliptic, elliptic], lanceolate, linear-lanceolate, linear, or filiform, flat or convolute at maturity, base truncate, margins entire [indistinctly undulate], apex acute.
terminal spikes;
flowers solitary in axils of ovate, lanceolate, or linear leaflike bracts (also in axils of middle and lower leaves and branches in C. ochotense and occasionally in some other species).
bisexual;
perianth segments absent or 1(–3), scalelike;
stamens 1–3(–5);
ovary superior;
stigmas and styles 2.
vertical;
embryo horseshoe-shaped or almost circular;
perisperm abundant.
structures: style bases at maturity forming characteristic bifid rostrum (“beak”) at apex of achenes [concealed by wing in some species], achenes largely exposed, vertical, sessile, convex to almost plane abaxially, plane, ± concave adaxially, lenticular, ovate, obovate, elliptic, or orbiculate [elongate], margins winged or wingless, apex acute, glabrous and shiny, or maculate and/or slightly verrucose;
wing (if present) with entire, undulate, or minutely erose-denticulate margins (in some species emarginate at apex, or long-adnate to style bases);
pericarp strongly accrescent to seed or small portions not accrescent, forming small whitish bladders (“warts”).
= 9.
Corispermum
Species ca. 65 (11 in the flora).
Mature fruits are important and usually necessary for reliable identification of Corispermum. Serial herbarium material showing variability is also desirable. The wing of a fruit should be observed and measured from the abaxial (dorsal) face of a fruit. When observed from the adaxial face, the pale margin marking the position of the hippocrepiform peripheral embryo could be confused for the true wing.
For a long time representatives of this genus were believed to be recently introduced to North America from Europe. In the treatment by N. J. Maihle and W. H. Blackwell (1978) only three species were reported for North America: Corispermum hyssopifolium Linnaeus, C. nitidum Kitaibel ex Schultes, and C. orientale Lamarck (all Eurasian). However, it is now clear from both recent taxonomic studies and fossil evidence that Corispermum was present in North America at least 38,000 years b.p. in Alaska and the Yukon, 11,000–14,000 years b.p. in Arizona and Utah, and ca. 4000 years b.p. in New Mexico (for details see C. O. Rosendahl 1948; J. L. Betancourt et al. 1984; J. V. Matthews Jr. 1982; S. B. Young 1982; S. L. Mosyakin 1995, 1997). Native American species of Corispermum are evidently closely related to eastern Asian (especially Siberian) ones, but not to native European taxa.
Although specific limits between related taxa in Corispermum are uncertain, a rather narrow species concept is accepted in the present treatment. The author is well aware of possible shortcomings and inconveniences of that approach and agrees with the opinion expressed by W. S. Judd and I. K. Ferguson (1999, p. 406): “It seems clear both that an extremely broad treatment of C. hyssopifolium is not justified, especially since the genus is indigenous in North America, and that a typological approach leading to the recognition of numerous arbitrarily separated microspecies is not useful.” My first intention was to make the treatment consistent with the prevailing Eurasian narrow species concept for the genus applied by M. M. Iljin (1929, 1936), P. Aellen (1961, 1964), M. V. Klokov (1960), M. Kitagawa (1935), Tsien C. P. and Ma C. G. (1979), and others. I also wanted to emphasize the unusual diversity of the native Corispermum taxa in North America. Unfortunately, virtually no experimental taxonomic or field ecological research has been done on taxa of the genus in Asia and North America, and I had no other choice but to rely almost exclusively on herbarium taxonomy and experience with Eurasian taxa. It remains the task of further studies to reveal the precise natural boundaries between North American species of Corispermum and their phylogenetic links to Eurasian taxa.
Because of common misidentifications in the past and the limited scope of the current treatment, which was based almost exclusively on herbarium specimens, data on exact distribution patterns of Corispermum species in North America remain deficient and tentative. Corispermum is most abundant in arid regions of Asia, with some species occurring in temperate and subarctic zones. Some species often occur as introduced far beyond their native ranges, and immature specimens are difficult to identify with certainty. Special taxonomic and floristic studies are needed in order to reveal the actual distribution of many Corispermum species in North America.
Excluded species:
Corispermum orientale Lamarck in J. Lamarck et al., Encycl. 2: 111. 1786
No specimens resembling typical Corispermum orientale were found in North American collections. However, small-fruited and almost wingless specimens of C. villosum may be confused with C. orientale.
Corispermum marschallii Steven, Mém. Soc. Imp. Naturalistes Moscou 5: 336. 1817
A specimen of Corispermum marschallii was found by the author at MO among North American specimens (mis)identified as C. hyssopifolium. However, the label is virtually illegible, and probably the specimen was misplaced. No other indication of occurrence of that unmistakable Eurasian species in North America has been found yet.
Corispermum sibiricum Iljin, Izv. Glavn. Bot. Sada S.S.S.R. 28: 649. 1929
Records of Corispermum sibiricum from the Great Plains (Great Plains Flora Association 1986) were based on misidentified collections of C. pallasii or C. americanum, which belong to the same subsection.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Fruits 1.8-3.2(-3.5) mm, wingless, or with barely visible narrow wing less than 0.1(-0.15) mm wide | → 2 |
1. Fruits 2.3-5.2 mm, wings 0.1-1 mm wide, if almost wingless then fruits 3.5-5.2 mm | → 3 |
2. Fruits broadly elliptic or obovate-elliptic to almost orbiculate, broadest at or slightly beyond middle, shiny, usually without warts and dark spots; inflorescences linear or indistinctly clavate, not condensed apically | C. hyssopifolium |
2. Fruits elliptic or obovate-elliptic, usually broadest beyond middle, dull, spotted and/or warty; inflorescences distinctly clavate or clavate-linear, rarely almost ovate, usually distinctly condensed distally | C. villosum |
3. Plants 5-15(-20) cm; fruits usually developed also at axils of middle and lower leaves and branches; arctic or subarctic | C. ochotense |
3. Plants 5-70 cm; fruits developed only in axils of inflorescence bracts; temperate regions | → 4 |
4. Fruits black or nearly so (immature fruits usually deep olive green), orbiculate-obovate to almost orbiculate, broadest near or slightly above middle, shiny, with out spots or warts | C. pacificum |
4. Fruits brown, yellowish brown, reddish brown, greenish brown, olive green (very rarely almost black, then more elongate, not orbiculate-ovate or orbiculate), shiny or dull, occasionally spotted or/and warty | → 5 |
5. Wings of fruits 0.7-1.0 mm wide; fruit body flattened | C. pallidum |
5. Wings of fruits absent or 0.1-0.6(-0.7) mm wide; fruit body somewhat to strongly convex abaxially, concave adaxially | → 6 |
6. Inflorescences at maturity narrowly linear or linear (rarely linear-clavate), lax, usually interrupted from base to apex; leaf blades narrowly linear or filiform | → 7 |
6. Inflorescences at maturity linear-clavate to ovate, rather dense or at least condensed towards apex; leaf blades narrowly lanceolate, linear-lanceolate, or linear | → 8 |
7. Fruits broadly elliptic or indistinctly obovate (usually broadest near or slightly beyond middle), shiny, never warty or spotted; leaves in mature plants often convolute; bracts ± uniform, usually narrower than fruits | C. nitidum |
7. Fruits obovate-elliptic (usually distinctly broadest beyond middle), shiny or dull, often spotted and/or warty; leaves usually flat, occasionally convolute in dry plants; bracts not uniform, proximal often much longer than distal, width equaling or wider than mature fruits (occasionally proximal leaflike bracts narrower than fruits) | C. americanum |
8. Fruits wingless or wings ca. 0.1-0.3 mm wide; fruit body usually strongly convex abaxially, plane to strongly concave adaxially | → 9 |
8. Fruits with wings (0.15-)0.2-0.6 mm wide, slightly convex abaxially (sometimes strongly convex in C. welshii), plane to slightly concave adaxially | → 10 |
9. Fruits (4.2-)4.5-5(-5.2) mm, elongate-obovate or obovate-elliptic, apex rostrate- triangular, usually maculate and/or warty | C. navicula |
9. Fruits (3.2-)3.5-4.5(-5) mm, obovate to oblong-obovate (elongate in var. pseudodeclinatum), apex rounded or broadly triangular, usually without spots and warts | C. hookeri |
10. Fruits broadly obovate-orbiculate or almost orbiculate (broadest near or slightly beyond middle), wings rounded, truncate, or indistinctly emarginate apically; inflo- rescences ovate or short-clavate (rarely oblong-clavate) | C. welshii |
10. Fruits usually obovate or obovate-elliptic, occasionally broadly obovate-elliptic, wings usually broadly triangular apically, rarely rounded; inflorescences usually clavate to clavate-linear | C. pallasii |
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