4. Plantago heterophylla Nutt. (small plantain)
Pl. 486 g, h;
Map 2223
Plants annual,
with slender taproots (these sometimes disappearing quickly, leaving only a
small patch of fibrous roots). Aerial stems absent or very short. Leaves in a
dense basal rosette, mostly lacking discrete petioles (but the bases usually
slightly expanded and sheathing), usually pale at the base, ascending or
sometimes spreading with age. Leaf blades (1–)3–9 cm long, 0.5–2.5 mm wide,
linear to threadlike (those of seedlings sometimes narrowly obovate), angled to
a sharply pointed tip, tapered at the base, the margins entire or with sparse,
spreading to loosely ascending, slender teeth, the surfaces glabrous or
sparsely to moderately pubescent with short, appressed hairs, appearing green
to dark green, with 1 main vein. Inflorescences 1 to several per plant,
terminal, elongate spikes, 1–6(–8) cm long, 2–4 mm in diameter, loosely
flowered (the axis visible between the flowers), the stalk 2–10 cm long, erect
or strongly ascending, sparsely appressed-hairy, the axis solid. Bracts 1.5–3.0
mm long, similar in length, about as long as to more commonly somewhat longer
than the flowers (mostly noticeably longer than the calyces), lanceolate to
ovate, with broad, translucent margins and a thickened, bluntly keeled, green
midnerve, rounded or angled to a bluntly pointed tip, glabrous. Cleistogamous
flowers usually ubiquitous (open flowers with spreading corollas rarely
intermingled with cleistogamous ones). Calyces deeply 4-lobed, 1.5–2.5 mm long,
slightly zygomorphic, oblong-ovate to obovate, rounded at the tip, the keel
glabrous, the relatively broad margins thin and papery. Corollas not noticeably
zygomorphic, the lobes 0.4–0.8 mm long, narrowly lanceolate to lanceolate with
a truncate base, sharply pointed at the tip, the margins entire, tan, all of
the lobes erect and overlapping at flowering, appearing beaklike at fruiting
(rarely those of a few flowers spreading during flowering). Stamens 2, the
anthers not horned. Fruits 1–3 mm long, narrowly ellipsoid, circumscissile
below the midpoint. Seeds mostly 10–25 per fruit, 0.5–0.8 mm long,
rhombic-ovate to rhombic-elliptic, the surface with a differentiated band on 1
side, but usually not appearing concave, otherwise coarsely pitted, dark brown
or black, shiny. 2n=12, 22. April–May.
Uncommon,
sporadic in the southern half of the state (eastern [mostly southeastern] U.S.
west to Missouri and Texas; Mexico). Old fields and open, sandy disturbed
areas.
The relationship
of P. heterophylla to P. elongata requires further study. Some
authors have suggested that the seed number per capsule does not work well to
distinguish the two taxa (Shinners, 1967). However, in a morphometric study of
the complex in Oklahoma, Hoggard (1998) concluded that a suite of quantitative vegetative
and floral characters also differs statistically between the two. He suggested
that eventually the two taxa might best be treated as varieties of a single
species, but concluded that more detailed research was necessary before
taxonomic changes could me made with confidence. Thus the present treatment
continues to maintain them as separate, but closely related species.
It should be
noted that the name P. hybrida W. Barton also requires further
evaluation. Although most botanists have treated it as a synonym of P.
elongata (including P. pusilla), Shinners (1967) took it to
represent an older name for the plants usually called P. heterophylla.
Rosatti (1984) correctly pointed out that the original description does not
mention seed number, thus the question of whether this name refers to plants of
P. elongata or P. heterophylla remains unresolved. If it should
prove to refer to plants currently called P. heterophylla, then P.
hybrida is the older name and has nomenclatural priority over P.
heterophylla.