8. Lappula Moench (stickseed,
beggars lice)
Plants annual or
rarely biennial, with short taproots. Stems 5–60 cm long, erect or ascending,
solitary or few to several, usually moderately branched above the midpoint,
moderately to densely pubescent with shorter and longer, fine, spreading to
ascending, often minutely pustular-based hairs. Leaves alternate and basal (the
lower leaves sometimes withered at flowering), sessile, the blade 1–8 cm long,
3–10 mm wide, linear to narrowly oblong or narrowly oblanceolate, short-tapered
to rounded at the base, rounded or angled to short-tapered to a bluntly or
sharply pointed tip, the surfaces moderately to densely hairy, without
noticeable lateral veins. Inflorescences usually paired, terminal on the
branches, sometimes also on short lateral branches and thus appearing axillary,
appearing as dense clusters at the start of flowering, then becoming elongated
into usually scorpioid, spikelike racemes, these sometimes appearing aggregated
into leafy panicles, the flowers usually with stalks 0.5–2.0 mm long, these not
elongating noticeably at fruiting, erect to loosely ascending, each flower
subtended by a small, lanceolate to linear bract. Calyces 5-lobed nearly to the
base, the lobes 1.5–2.5 mm long at flowering, becoming elongated to 2–4 mm at
fruiting, linear to oblong-lanceolate, moderately to densely pubescent with
stiff, ascending, pustular-based hairs. Corollas small, broadly funnelform to
somewhat trumpet-shaped, white or pale blue, the tube about as long as the
calyx, the throat with scalelike appendages. Stamens inserted at about the
midpoint of the tube, the filaments very short, the anthers oblong, not
exserted from the corolla. Ovary deeply 4-lobed, the style very short, not
exserted from the corolla, usually persistent but inconspicuous at fruiting,
the stigma capitate, unlobed. Fruits dividing into mostly 4 nutlets, these 2–3
mm long, erect, more or less angular-ovoid with a relatively sharp ventral
keel, attached to the very narrowly pyramidal gynobase along the ventral keel,
the attachment scar slender and elongate, bluntly to sharply pointed at the
tip, the dorsal surface with 1 or 2 rows of tapered, apically barbed tubercles,
these sometimes expanded and fused into a narrow, irregular ridge at the base,
otherwise with minute warts or tubercles, brown. Twelve to 40 species, North
America, Europe, Asia; introduced nearly
worldwide.
The two species
of Lappula in Missouri
are very similar in overall morphology. As discussed by Higgins (1979) and
Al-Shehbaz (1991), the innate morphological variability of populations has
resulted in the segregation of numerous species and infraspecific taxa from
both of the species treated below. The presence of many intermediate plants for
all of the characters said to delineate these taxa argues against their
recognition. The genus is closely related to Hackelia, and the barbed
nutlets in both genera facilitate dispersal by hooking into the fur (or
trousers) of creatures coming into contact with fruiting plants.