Flora of Dominica, Part 2 - Smithsonian Institution Libraries

32 ASTERACEAB SMITHSONIAN CONTRIBUTIONS TO BOTANY
26. Inflorescence compounded of multiple involucrate heads (with secondary
heads).
27. Compounded heads spheroidal; leaves petiolate, whitish beneath, pappus
short, without awns ...................... Rolandra
27. Compounded heads not spheroidal; leaves tapered to k sessile base, not
white beneath; pappus of 5 long bristles.
28. Pappus awns straight; secondary heads subtended by broad bracts
............................. Elephantopus
28. Pappus awns contorted, secondary heads not subtended by extremely
broad bracts ................... Pseudelephantopus
26. Heads not compounded.
29. Heads with receptacular bracts (pales) among the florets.
30. Pappus of many capillary bristles .............
Neurolaena
30. Pappus of scales, awns, or lacking.
31. Heads solitary; peduncles swollen below heads ...... Tithonia
31. Heads in branching panicles; peduncles not swollen below heads.
32. Marginal florets only fertile (setting achenes); achenes attached to
a pair of male florets and their pales, without lateral wings or
apical awns ..................... Parthenium
32. Florets all fertile (setting achenes); achenes not forming complexes
with adjacent florets, with marginal wings and apical
awns ......................... Verbesina
29. Heads without receptacular bracts (pales) among the florets.
33. Pappus without capillary bristles.
34. Heads axillary; leaves finely serrate; pappus a smooth collar
.............................. Struchium
34. Heads terminal, subtended by several leaves; leaves coarsely dentate
or lobed; pappus deciduous, lacking, or a serrulate fringe.
35. Heads closely subtended by leafy bracts; achenes prismatic;
pappus deciduous or lacking ...........
Centratherum
35. Heads not closely subtended by leafy bracts; achenes biconvex;
pappus a short, serrulate collar .............
Egletes
33. Pappus of many capillary bristles.
36. Involucre 1-seriate.
37. Heads solitary, >1 cm long; leaves entire .....
Porophyllum
37. Heads in branching cymes or corymbs, much shorter; leaves lyrate
to dentate.
38. Heads conspicuously radiate .............. Senecw
38. Heads without ray-florets (all florets disciform).
39. Involucre without bracteoles; all florets bisexual . . Emilia
39. Involucre subtended by linear bracteoles; outer florets
pistillate ..................... Erechtites
36. Involucre 2-5-seriate.
40. Heads few or solitary; leaves in a basal rosette; female florets with
ligulate limbs.
41. Leaves lobed or dentate; achenes prismatic and beaked; disk
florets slightly bilabiate .............. Chaptalia
41. Leaves entire; achenes biconvex, not beaked; disk florets not
bilabiate ....................... Erigeron
40. Heads numerous in complex inflorescences; none of florets with
ligulate limbs.
42. Heads heterogamous (2 types of florets in each head).
43. Heads small (to 0.5 mm long); achenes biconvex ......
........................... Conyza