PLATE VII. 



P. I. X. spinosum L. Eggert (Hb. Mo. 720835). 



F. 2. X. strumarium L. Brandegee (Hb. Calif. 131246). 



F. 3. X. chinense Mill. Greenman 47 (Hb. Field 189512; topotype; atypic in hav- 

 ing prickles slightly pubescent at base.) 



F. 4. X. cyhndricum Millsp. and Sherff. Small and Huger (Hb. Field 401312; type). 



F. 5. X. globosum Shull. Shull (Hb. Field 477328; lineal descendant of type mate- 

 rial). 



F. 6. X. arcuatum Millsp. and Sherff. Lucy (Hb. Field 4953; type). 



F. 7. X. curvescens Millsp. and Sherff. Eggleston 1420 (Hb. Gray; type). 



F. 8. X. leptocarpum MiJJsp. and Sherff. Jones (Hb. Field 430860; type). 



F. 9. X. Wootoni Cockll. ex De Vries. T. D. A. Cockerell, Las Vegas, New Mexico, 

 Oct. 4, 1901 (Hb. N. Y.; authentic material from author). 



F. 10. X. cenchroides Millsp. and Sherff. Reverchon 2332 (Hb. Mo. 85563; type). 



F. ii. X. inflexum Mack, and Bush. Bush 1916 (Hb. Mo. 85520; type material). 



F. 12. X. pennsylvanicum Wallr. Lansing 3532 (Hb. Field 346590). 



F. 13. X. calvum Millsp. and Sherff. Baker 1760 (Hb. Calif. 131236; type). 



F. 14. X. palustre Greene. Walker 973 (Hb. Calif. 128022). 



F. 15. X. australe Millsp. and Sherff. Palmer 275 (Hb. U. S. 463216; type). 



F. 16. X. echinatum Murr. Miss M. E. Blatchford, Prouts Neck, Me., Sept., 1898 

 (Hb. Gray). 



F. 17. X. italicum Mor. B. L. Robinson, Springfield, Vt., Sept. 16, 1899 (Hb. Gray). 



F. 1 8. X. acerosum Greene. Lunell 80 (Hb. Gray). 



F. 19. X. oviforme Wallr. Suksdorf 189 (Hb. Gray). 



F. 20. X. speciosum Kearn. Bush 1185 (Hb. Mo. 85380; type material of X. 

 bubalocarpon Bush). 



F. 21. X. campestre Greene. Heller 11629 (Hb. Gray; topotype). 



