PREFACE. 



The accompanying paper by Mr. Paul C. Standley, Assistant Cura- 

 tor in the United States National Herbarium, is an account of the 

 Mexican and Central American plants of the family Allioniaceae. 

 It follows a similar paper dealing chiefly with the representatives 

 of the family in the United States, published in Volume XII of this 

 series. 



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The present paper is the result of field work and of the study of 

 material found in all the larger herbaria of this country. As in many 

 other families of Mexican plants, the material of the Allioniaceae 

 was found in a very confused state. The total number of represen- 

 tatives of the family reported from the region under discussion is 

 113, several of which are described here for the first time. 



Frederick V. Coville, 

 Curator of the United States National Herbarium, 



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