PREFACE. 



The third installment of the Trees and Shrubs of Mexico, by 

 Mr. Paul C. Standley, Assistant Curator of the United States 

 National Herbarium, treats the families Oxalidaceae to Turnera- 

 ceae, both inclusive. Several of the largest and most important 

 groups of Mexican trees are included, such as the Meliaceae, which 

 contains the true mahoganies of the genus Sivietenia; the Euphor- 

 biaceae, or spurge family; the Malvaceae, or mallow family; and 

 the Sterculiaceae, among whose representatives is the cacao, Theo- 

 hroma cacao^ perhaps the most important economically of all the 

 native Mexican trees. 



The accounts of the families Meliaceae and Polygalaceae have 

 been furnished by Dr. S. F. Blake of the United States Department 

 of Agriculture. 



Frederick V. Coville, 

 Curator of the United States National Herharium. 



