INTRODUCTION. 
The greater part of the botanical collections made by Dr. J. M. Bigelow, in the Pacific 
Railroad Survey, under the charge of Captain Whipple, were submitted to me for examination, 
in accordance with the instructions of the War Department. The plants that were collected 
before reaching Fort Smith, on the western borders of Arkansas, are of comparatively little 
interest, and are not included in the following list. The surveying party, in proceeding from 
Fort Smith to Albuquerque, travelled near the Canadian river, through the Indian territory 
and northern Texas ; thence through northeastern New Mexico to the Rio Grande. This river 
was crossed on the 10th of November, at which time the flowering season of most plants had 
passed ; and the explorations continued through western New Mexico, chiefly between the 
parallels of 35? and 36°, to the Great Colorado, which was reached on the 28th of February. 
The most interesting region of this part of the route is the valley. of Williams' river, (com- 
monly called Bill Williams” Fork,) a tributary of the Colorado. Some of the most remarkable 
plants of the collection were found here, and it is a matter of regret that a country so rich and 
peculiar in its Flora (and 1 am informed by Professor Baird that its Fauna is equally remark- 
able) was not visited at a more favorable season. From the Colorado the route was across the 
California desert to the Cajon Pass, in the southern part of the Sierra Nevada; thence through 
Coco Mungo and Los Angeles to San Pedro, on the Pacific coast. Here the surveys of Captain 
Whipple terminated ; but Dr. Bigelow remained in California until near the first of June, and 
improved the time in exploring considerable portions of the valleys of the Sacramento and San 
Joaquin, as well as numerous tributaries of those rivers. His ample collections were brought 
home in perfect order, and the following report affords abundant proof of the zeal and success 
with which he labored. A number of new genera, and more than sixty new species, have been 
discovered by Dr. Bigelow, and he has added much valuable information upon many heretofore 
imperfectly known plants. 
The observations of Dr. Bigelow upon the geographical botany of the regions explored are 
interesting, and are embodied by him in a separate memoir, as also are his notes upon the more 
interesting forest trees of the country. 
The Cactaceæ collected in the Expedition have been elaborated conjointly by Dr. Engelmann 
and Dr. Bigelow, and are described by them in a separate portion of Captain Whipple's report. 
The Composite and Scrophulariacee were described by my friend "Dr. Gray, to whom I am 
indebted also for much valuable aid in drawing up this catalogue, as will be seen by the fre- 
quent quotation of his manuscript names in the following pages. The drawings were, with few 
exceptions, executed by Sprague and Riocreux, two of the most skilful botanical artists now 
living. All the engraving has been done upon stone by Prestele, who excels in this branch of 
the art. 
ge JOHN TORREY. 
New York, January 12, 1857. 
