190 University of California Publications in Botany [Vol. lo 



INTRODUCTION 



In monographing the Calif ornian species of Lotus one must consider 

 first the limits of the species, and, second, the unity of the group and its 

 relationships to Old World forms. The early publications of Bentham 

 (1829, 1837), of Gray (1863), and of Watson (1876) dealing with 

 American species are inadequate to meet the present needs, as the 

 Avork of later students has resulted in the accumulation of much 

 material, and in additions to the number of described species. The 

 somewhat heterogeneous assemblage of American species is in many 

 respects similar to the Old World group, but has been treated in 

 diverse ways by the various authors. An Enumeration of the North 

 American Loti was published by Greene in 1890. Although com- 

 paratively few species have been described since, the need of further 

 investigation is still great, as Greene's diagnoses are commonly brief 

 and practically ignore the variations present within many of the 

 species. 



Geographical Distribution 



The New World Loti comprise a large group of species, limited, 

 almost without exception, to western North America, extending from 

 British Columbia to Mexico and Lower California, but, in one case, 

 reaching as far south as Chile. Only one native species has been cited 

 for the eastern, and one for the middle United States, the latter being 

 abundant in the Pacific Coast states. More species are found growing 

 in California than in any other one state. In the northern part of 

 the state occur species common to British Columbia, Washington, 

 Idaho, and Oregon ; in the southern part and in the islands off the 

 coast appear many species which occur also in Lower California ; and 

 in the eastern and southeastern parts, especially in the regions of the 

 Mohave and Colorado deserts, are found several species whose range 

 extends into Nevada, Arizona, and Mexico. 



The Old World species of Lotus have a widespread geographical 

 distribution. They are of most common occurrence in those parts of 

 Europe, Asia, and Africa adjacent to the Mediterranean Sea, but they 

 appear also in northern Europe, southern Africa, and montane Asia. 

 In Australia the genus is represented by one indigenous species. 



