2. Picris rhagadioloides (L.) Desf. (bitterweed)
P. altissima Delile
Pl. 260 n–o; Map
1089
Plants annual, taprooted.
Stems 20–100 cm long, moderately to densely pubescent with spreading,
barb-tipped hairs, usually also sparsely to moderately pubescent with minute,
appressed, branched hairs. Basal and lower stem leaves 3–15 cm long. Involucre
7–12 mm long, the inner series of bracts thickened and hard at fruiting, the
basal portion becoming wrapped around the outer series of fruits (these usually
becoming dispersed tardily, remaining with the involucre after the inner fruits
have been shed), pubescent with a central band of spreading, barb-tipped hairs,
usually also pubescent with sparse to moderate, minute, appressed, branched
hairs. Corollas 0.8–1.5 cm long. Pappus 4–6 mm long (that of the outer florets
sometimes shorter elsewhere). Fruits 2.5–3.0 mm long. 2n=10. June–September.
Introduced,
known thus far only from St. Louis County (native of Europe, Africa;
introduced). Railroads.
The correct name
for this plant remains somewhat controversial. Traditionally, this species has
been called P. sprengerana (L.) Poir. in most of the botanical
literature (Steyermark, 1963), but as noted by Lack (1974) and Greuter (2003),
that name instead applies to an Old World species of Hieracium. Lack
(1974) referred to the species as P. integrifolia Desf., but Holzapfel
(1994) suggested that this epithet was not validly published and used the name P.
altissima. Most recently, Greuter (2003), noted that the name P.
rhagadioloides is the oldest valid name for the taxon, rejecting Lack’s
(1974) earlier arguments against the acceptance of this name.