186 CAMPAXULALES 



2. Gaertneria discolor (Xiitt.) Kuntze. 



In dry soil in the western part of the state. Dix. 



3. Gaertneria tomentosa (A. Gray.) Kuntze. 



In low prairies along streams. Axtell; Franklin; Hastings; Minden. 



4. Xanthium. 911. 



Burs nearly glabrous, beaks straight. 1. X. glabratum. 

 Burs not glabrous, beaks hooked or incurved. 

 Burs 15-25 mm, long, about half as thick or less. 



Prickles not hispid or scarcely so. 2. X. canadense. 



Prickles hispid to about the middle. 3. X. commune. 



Burs 10-15 mm. long, 6-9 thick, its prickles bristly-hispid nearly to 



the hooked apex. 4. X. glanduliferum. 



1. Xanthium glabratum (DC.) Britton. 

 Nebraska according to Britton's Manual. 



2. Xanthium canadensis Mill. Cocklebur. 

 Not common, most of our cockleburs belong to the next species. Ken- 

 nedy; Red Cloud; Valentine. 



3. Xanthium commune Britton. Common Cocklebur. 

 A common weed all over the state. Grand Island; Lincoln; Red 

 Cloud; St. Paul; Valentine; Wahoo. 



4. Xanthium glanduliferum Greene. Glandular Clot-bur. 

 Fremont; Long Pine; Nebraska City; Red Cloud; Whitman. 



Tribe 7. HELENIEAE. 



Bracts of the involucre petaloid with scarious tips and margins. 

 Leaves pinnatifid, flowers white or yellow, rays none. 



1. Hymenopappus. 

 Leaves entire, flowers purple, rays present or wanting. 



2. Polypteris. 

 Bracts of the involucre herbaceous. 



Leaves palmately divided into 2-5 narrow segments. 



3. Picradeniopsis. 

 Leaves not palmately divided. 

 Foliage not dotted with oil-glands. 

 Receptacle naked, rays yellow. 



Bracts of the involucre appressed, leaves not decurrent on 



the stem. 4. Tetraneuris. 



Bracts of the involucre spreading or reflexed at maturity, 



leaves usually decurrent on the stem. 5. Helenium. 



Receptacle bristly, rays in our species purple at least at the 



base. 6. Gaillardia. 



Foliage dotted with oil-glands. 



Leaves dissected, involucral bracts partly united. 7. Boebera. 

 Leaves entire, linear, bracts separate. 8. Pectis. 



1. Hymenopappus. 1006. 



Corolla white, heads 8-12 mm. broad, biennials. 



Achene puberulent, pappus shorter than the width of the achene. 



1. H. corymbosus. 



