--39.

38b. Leaves hairy on the upper side --40.

39a. Stem glabrous, leafless or with one or two leaves
=Hawkweed, Hieracium venosum.=

39b. Stem with several leaves, hairy below
=Hawkweed, Hieracium marianum.=

40a. Leaves with short scattered hairs above
=Hawkweed, Hieracium gronovii.=

40b. Leaves and stem densely covered with very long hairs
=Hawkweed, Hieracium longipilum.=

41a. Leaves glabrous =Hawkweed, Hieracium paniculatum.=

41b. Leaves very hairy =Hawkweed, Hieracium scabrum.=

42a. Bracts of the involucre smooth (5-20 dm. tall; summer and
autumn) (Sow Thistle) --43.

42b. Bracts of the involucre hairy --44.

43a. The clasping leaf-bases acute =Sow Thistle, Sonchus oleraceus.=

43b. The clasping leaf-bases rounded =Sow Thistle, Sonchus asper.=

44a. Heads 2.5-5 cm. broad; involucre 2 cm. long (4-10 dm. high)
=Sow Thistle, Sonchus arvensis.=

44b. Heads 1-2 cm. broad; involucre 6-10 mm. long (3-6 dm. high;
summer) =Hawksbeard, Crepis tectorum.=

45a. Leaves or involucre or both spiny (thistles, burdock, etc.) --46.

45b. Neither leaves nor involucre spiny --60.

46a. Leaves 1-4 dm. broad, not spiny (flowers purple or white;
summer) (Burdock) --47.

46b. Leaves narrower, not spiny --48.

47a. Diameter of involucre at flowering time 3-5 cm. (1-3 m. high)
=Burdock, Arctium lappa.=

47b. Diameter of involucre at flowering time 1.5-3 cm. (5-15 dm. high)
=Burdock, Arctium minus.=

48a. Each head 1-flowered; heads aggregated in a globular
head-like cluster (1-2 m. high; flowers blue or white, summer)
=Globe Thistle, Echinops sphaerocephalus.=

48b. Each head many-flowered --49.

49a. Principal involucral bracts with stout spreading spines 2-4 cm.
long (5-15 dm. high; flowers purple, summer)
=Milk Thistle, Silybum marianum.=

49b. Principal involucral bracts with slender spines or none --50.

50a. Pappus feathery; receptacle bristly (summer and autumn)