v iJi INTRODUCTION. 



two thousand, and it was thought that the work of determining and describ- 

 ing them would not occupy more than a year or two. The co-operation of 

 distinguished specialists throughout the country was secured, and various 

 portions of the collections placed in their hands to he worked up. It 

 is, however, at the Herbarium of Harvard University, and under the 

 supervision of Professor A. Gray, that most of the material has thus far 

 been elaborated. The collections made by the Survey were there arranged 

 by Professor Brewer, and the new species of the Polypetalce and Gamo- 

 petalce were described by Professor Gray in various communications made 

 to the American Academy of Arts and Sciences, and published in their 

 Proceedings.* 



In this work it was necessary that the material which had accumulated 

 during the many years in which California had been botanically explored 

 by various Government expeditions, both American and foreign, and by 

 numerous private collectors, should be passed under review. It was equally 

 necessary that the mass of literature already accumulated in relation to this 

 Flora, and scattered through hundreds of volumes, which in many cases are 

 not to be obtained except with great difficulty, should be thoroughly ex- 

 amined. Much the largest portion of this material, both of books and 

 plants, was accessible at the Herbarium in Cambridge ; and, where the collec- 

 tions in this country were deficient, both Dr. Gray and Dr. Engelmann were 

 enabled to supply deficiencies and make the necessary comparisons, during 

 visits to Europe, and especially to the great storehouse of the world's 

 botany at Kew. While this work of description and comparison went on, 

 much new material was constantly coming in, chiefly through several zeal- 

 ous private collectors, who of course had to send their plants to Cambridge 

 for determination. Thus it happened, that, as the amount of material to 

 be worked over was constantly increasing, so the time required for the work 

 was also greatly expanded. The Survey not being able to pay any one for 

 devoting his whole time to this investigation, the year 1874 had been 

 reached and the printing had not been begun. The Legislature of 1873 - 74 

 put an end to the work by refusing any further appropriations for the 

 Survey, and the present volume would have remained unpublished, had it 

 not been for the generosity of a few citizens of San Francisco, who came 

 forward and placed in the hands of the late State Geologist a sum sufficient 

 * See Proceedings Am. Acad. Vol. VI. 519, and VII. 327. 



