PREFACE. 
There is presented herewith a second installment of studies by 
Mr. Paul C. Standley, of the United States National Herbarium, upon 
the flowering plants of tropical America. The new species described 
and the changes of nomenclature proposed are largely the result of 
work upon certain groups, chiefly Rubiaceae, Malvaceae, and Legu- 
minosae, as represented in the extensive collections obtained recently 
in Panama during the progress of the Smithsonian Biological Survey 
of the Panama Canal Zone. A large part of the paper consists of 
descriptions and nomenclatorial changes in the Amaranthaceae and 
Allioniaceae incidental to monographic work upon these families. 
Two new genera are proposed in the Malvaceae. 
FREDERICK V. CovILLE, 
Curator of the United States National Herbarium. 
II 
