2. Phacelia covillei S. Watson
Map 1917
Plants
relatively slender annuals. Stems 7–30 cm long, unbranched or more commonly
few- to several-branched at the base and above, loosely to strongly ascending
from a sometimes spreading base, moderately pubescent with stiff, loosely
ascending to spreading, nonglandular hairs toward the base, these grading into
dense, shorter, gland-tipped hairs toward the tip (median portion with mostly
nonglandular hairs, a few gland-tipped hairs occasionally also present). Basal
(and lower stem) leaves often persistent at flowering, the blade 1–3 cm long,
broadly ovate to broadly elliptic or oblong-elliptic in outline, pinnately
compound with 3–7 pinnae, these unlobed or (especially the terminal pinna)
mostly moderately to deeply 2- or 3-lobed and sometimes also with a few
additional teeth or smaller lobes, the teeth or lobes sharply to bluntly
pointed or occasionally rounded at the tips, the surfaces sparsely to
moderately pubescent with more or less appressed, stiff hairs. Stem leaves all
moderately to long-petiolate, the blade 1–4 cm long, progressively less divided
toward the stem tip, the uppermost leaf blades often irregularly 3-lobed, the
leaflets or lobes sharply to bluntly pointed or occasionally rounded at the
tips, the terminal lobe of at least the uppermost leaf (immediately below the
lowermost flower) narrowly angled or tapered at the base, the pubescence
similar to that of the basal leaves. Inflorescences with only 2–6 flowers, the
axis and flower stalks densely glandular-hairy, sometimes also with scattered
nonglandular hairs, the stalks spreading to downward-arched or pendant at
fruiting. Calyces 3–7 mm long, the lobes with the margins and surfaces
pubescent with mostly nonglandular hairs (glandular hairs more frequent at the
calyx base). Corollas 2–4(–5) mm long, narrowly bell-shaped to nearly
cylindrical, pale lavender to light purple, the margins entire, the outer
surface glabrous. Stamens not exserted, the filaments 1.5–2.0 mm long,
glabrous. Ovary with 4 ovules. Style branched to about the midpoint. Fruits 4–6
mm long, the surface usually irregularly swollen (distended by the seeds),
2–4-seeded. Seeds 2.0–2.5 mm long, broadly ovoid-angled to nearly globose,
finely ridged, brown. 2n=28. April–May.
Uncommon, known
thus far only from single sites in Pulaski and Texas Counties (Maryland to
North Carolina west disjunctly to Indiana, Illinois, and Missouri). Bottomland
forests, mesic upland forests in ravines, and bases of bluffs.
Chuang and
Constance (1977) were the first to document that plants called P.
ranunculacea exhibit two distinct chromosome numbers in the eastern and
western portions of the overall range, but they were not able to distinguish
the two cytotypes morphologically. Sewell and Vincent (2006) showed that the
eastern and western populations could be distinguished statistically based on a
suite of subtle characters. By linking these relatively cryptic morphological
differences to the different ploidy levels, they were able to use herbarium
specimens to better circumscribe the ranges of the two cytotypes. Although the n=14
cytotype is mostly restricted to the eastern United States, there are scattered
disjunct occurrences within the range of the n=6 cytotype in southern
Indiana, southern Illinois, and southern Missouri. Because they could
distinguish two entities morphologically and these entities have different base
chromosome numbers, Sewell and Vincent (2006) chose to recognize them as
distinct species. The underlying evolutionary relationship between the two is
not understood and there are no data to address the conjecture that the high
chromosome number in P. covillei is an indication of past hybridization
between P. ranunculacea and some other species of Phacelia.