1889.] BOTANICAL GAZETTE. 151 



Peoria, 111. It is evidently a hybrid from this species and 

 Bidens frondosa. The awns are downwardly barbed, and 

 the marginal hairs upwardly turned, as in B. frondosa, while 

 the rays and leaves are those of C. aristosa. 



C. invohicrata Nutt. is said to have achenia with two short 

 acute teeth, but was not seen. It is closely related to the 

 last through its variety. Fig. 33 is probably a hybrid from 

 this species and Bidens frondosa, collected by G. H. French 

 in 111., in 1878. 



C. bidentoides Nutt. Achenia linear to narrowly cuneate, 

 4 to'5 lines long (largest of the genus), with two prominent 

 awns I to f their length, slightly spreading, and minute awns 

 from the lateral angles. (Fig- 29.) 



Dr. Vasey collected near Washington, D. C, Sept. 23, 

 1888, a peculiar hybrid from this species and Bidens connata, 

 which has the awns of both Coreopsis and Bidens, that is, 

 they are hispid upward or downward or both ways. 



C. discoidca Torr. & Gray. Achenia linear-oblong to 

 cuneiform, 2 to 3 lines long ; awns more or less prominent, 

 erect or slightly spreading. (Figs. 30 a and 30 b) 



Explanation of Plate XVI.— All drawings X10. Fig. 1. C. nuda- 

 ta. Fig. 2. C. gladiata. Figs 3, 4, 5. G. angustifolia (the first two from 

 the same head. Fig. 6. C. Leavenworthii. Fig. 7. 0. Atkinsonia. Fig. 

 8. C. cardaminefolia. Fig. 9. C. tinctoria. Fig. 10. C. rosea. Fig. 11. C. 

 Drummondii. Figs. 12, 13. C. coronata. Fig. 14. C. grandiflora. Fig. 

 15. C. pubescens. Fig. 16a, 166. C. auriculata. Fig. 17. C. palmata. Fig. 

 18. C. verticillata. Fig. 19. C. delphinifolia. Fig. 20. C. senifolia. Fig. 

 21. C. tripteris. Fig. 22. C. latifolia. Fig. 23. C. aurea. Fig. 24. C. au- 

 rea, var. subintegra. Figs. 25, 20. C. trichosperma. Fig. 27. C. aristosa. 

 Fig. 28. C. aristosa, var. mutica. Fig. 29. C. bidentoides. Fig. 30a, 306. 

 C. discoidea (from same head). Fig. 31. C. aristosa X Bidens chrysan- 

 themoides. Fig. 32. C. aristosa X Bidens frondosa. Fig. 33. C. mvolu- 

 crata X Bidens frondosa. Figs. 11, 14, 15, 166 represent the ventral side 

 all others show the dorsal. 



Department of Agriculture, Washington, D. C. 





BRIEFER ARTICLES. 



Sensitive stamens in Compositae.-It is well known that the flowers of 

 several species of Compositse-are sensitive, among the leading of which 

 are the centaureas ana" thistles. This fact, together with the great simi- 

 larity of floral structures, has led me to look for movements in other spe- 

 cies. Considerable quantities of the flowers to be studied were collected, 



