PLANTS OF IOWA 223 



28940. H. scabrum, Michx. Rough Hawkweed. 



On rather open wooded slopes. 

 28946. H. longipilum, Torr. Long-bearded Hawkweed. 



Sandy prairies. 

 NABALUS, Cass. 



2895. N. albus, (L.) Hook. Rattlesnake-root. 

 Common in rocky woods. 



2895a. N. asper, (Michx.) T. & G. Rough White-lettuce. 

 Frequent on prairies. 



2895Z>. N. racemosus, (Michx.) DC. Glaucous White-lettuce. 

 On moist prairies. 



AMBROSIACE^I. RAGWEED FAMILY. 

 IVA, L. 



2896. /. xanthiifolia, (Fresn.) Nutt. Burweed Marsh Elder. 

 In moist prairie soils, becoming a common weed. 



AMBROSIA, L. 



2897. A. trifida, L. Great Ragweed. 



A common weed in low places and along roadsides. 



2898. A. trifida integrifolia, (Muhl.) T. & G. Entire-leaved 



Ragweed. 

 This variety is found in dry places. 



2899. A. artemisice folia, L. Ragweed. 



A common weed, along roads, and in fields. 



2900. A. psilostachya, DC. Western Ragweed. 

 Common in dry sandy soil. 



XANTHIUM, L. 



2901. X. gldbratum, (DC.) Britton. Burweed. 

 Banks of rivers, frequent. 



2902. X. canadense, Mill. American Cocklebur. 

 A common weed. 



2903. X. echinatum, Murr, Beach Clotbur. 

 Infrequent. 



COMPOSIT-ffl. THISTLE FAMILY. 



VERONIA, Schreb. 



2904. V. noveboracensis, (L.) Willd. Flat Top. 

 In moist soil. 



