PREFACE, 
The present number of the Contributions, by Dr. Francis W. 
Pennell, of the New York Botanical Garden, consists of an account of 
several genera of the family Scrophulariaceae as represented in the 
central Rocky Mountain States. It is based upon extensive field 
work carried on by the author in the region covered, and upon a 
critical study of material found in the larger American herbaria. 
The greater part of the paper relates to the genus Pentstemon, a large 
and difficult group containing many species which are among the 
most characteristic and attractive members of the Rocky Mountain 
flora. Because of the intensive character of the study, it has been 
Possible to indicate with unusual precision the range, habitat, and 
period of flowering of most of the species, and for the same reason it 
has been found necessary to describe a considerable number of them 
as new. 
Freverick V. Covit1z, 
Curator of the United States National Herbarium. 
Ii 
