34a. Heads 2.5 cm. in diameter, or larger --35. 34b. Heads 1-2 cm. in diameter (4-10 dm. high) --37. 35a. Leaves all basal (1-4 dm. high) =Hawkweed, Hieracium pilosella.= 35b. Stem-leaves present (4-15 dm. high) --36. 36a. Leaves rounded at the sessile base =Hawkweed, Hieracium canadense.= 36b. Leaves narrowed toward the base =Hawkweed, Hieracium umbellatum.= 37a. A rosette of basal leaves conspicuous at flowering time --38. 37b. No rosette of basal leaves at time of flowering --41. 38a. Leaves glabrous on the upper side --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.=