PEEFACE. 



The present part of volume 23 of the Contributions is a second 

 nstallment of the Trees and Shrubs of Mexico, by Mr. Paul C. 

 Standiey, assistant curator of the United States National Herbarium. 

 ?his portion of the work extends from the oak family to the bean 

 amily, both inclusive. Some of the largest and most important 

 ;roups of Mexican plants are included in the families here treated, 

 ^hich contain many species of economic value. The account of the 

 aks has been prepared by Dr. William Trelease, of the University 

 f Illinois. 



FltEDEmCK V. COWLLE, 



Curator of the United States National Herbarium. 



iir 



