VI.-CONTRIBUTIONS FROM THE U. S. NATIONAL HERBARIUM. 



Volume VIII. 



Part 1. Studies of Mexican and Central American plants. By J. N. 

 Rose. 



pp. 1-55, 12 pis., 11 tigs. 



Part 2. Economic plants of Porto Rico. By O. F. Cook and G. N. 

 Collins. 



pp. 57-269, 48 pis., 2 figs. 



Part 3. A stud}^ of certain Mexican and Guatemalan species of Poly- 

 podium. By William R. Maxon. 



pp. 271-280, 2 pis. 



Part 4. Studies of Mexican and Central American plants. By J. N. 

 Rose. 



pp. 281-339, 10 pis., 5 figs. 



Volume IX. 



The useful plants of the island of Guam, with an introductory account 

 of the ph3'sical features and natural history of the island, of the 

 character and history of its people, and of their agriculture. By 

 William E. Safford. 



pp. 1-404, 70 pis. 



Volume X. 

 Part 1. North American species of Festuca. By Charles V. Piper. 



pp. 1-48, 15 pis. 



27 



