Family ASTERACEA 195 
Tribe 9. SENECIONEZ. 
Leaves opposite, rays yellow. 1. Arnica. 
Leaves alternate. 
Rays none, flowers white or whitish. 
Marginal flowers pistillate, the central ones perfect, plants with 
a rank smell. 2. Erechtites. 
All the flowers perfect, sap milky. 3. Mesadenia. 
Rays present, yellow. 4. Senecio. 
1. Arnica. 1022. 
1. Arnica cordifolia Hook. 
Western Nebraska, according to Britton’s Manual. 
2. Erechtites. 1023. 
1. Erechtites hieracifolia (L.) Raf. Pilewort. 
In the eastern part of the state, not common. Lincoln. 
3. Mesadenia (Cacalia). 1023. 
Glaucous; stem terete; leaves lobed or incised. 1. M. atriplicifolia. 
Green, not glaucous; stem striate angled; leaves entire or denticu- 
late, not lobed. 2. M. tuberosa. 
1. Mesadenia atriplicifolia (L.) Raf. Pale Indian Plantain. 
In woods in the eastern part of the state. Nebraska City; Richard- 
son county. 
2. Mesadenia tuberosa (Nutt.) Britton. Indian Plantain. 
In low prairies in the eastern part of the state. Lincoln; Nebraska 
City; Wahoo. 
4. Senecio. 1024. 
Groundsels. 
Basal leaves neither linear nor parted into linear segments. 
Heads 10-14 mm. high; plant tomentose when young, soon glab- 
rous. 1. S. integerrimus. 
Heads 6-10 mm. high; stems often persistently tomentose. 
Basal leaves entire or rarely somewhat repand, densely and per- 
sistently whi‘e-tomentose to the inflorescence. 2. S. canus. 
Basal leaves, at least some of them, pinnatifid or crenate. 
Some of the basal leaves pinnatifid, persistently tomentose. 
3. S. plattensis. 
Basal leaves crenate, often purple; leaves glabrous or nearly 
so; stems often woolly, especially below. 4. S. pauperculus. 
Basal leaves linear or parted into linear segments. 
Basal leaves linear-cuneate, 4-6 mm. wide, the upper leaves usually 
laciniate or pinnatifid. 5. S. densus. 
All the leaves linear or parted into linear segments. 
Leaves all linear, entire, 1-3 mm. wide. 6. S. spartioides. 
Leaves, at least some of them, parted into 3-9 linear segments. 
7. S. riddellii. 
1. Senecio integerrimus Nutt. 
In moist soil in the eastern part of the state. Ainsworth; Lincoln; 
Ponca; Valentine; Whitney. 
2. Senecio canus Hook. 
Senecio purshianus Nutt. 
