300 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 13 



It may also be noted that a small number of suErutescent or woody 

 shrubs of the mainland frequently have exceptionally long, trailing 

 or procumbent branches on the islands. Among these are Cereus Emoryi, 

 Brickellia californica, and Artemisia californica. Other differences in 

 suflrutescence or pubescence will be treated in the following section. 

 Among many other plants there are minor differences in peduncle length, 

 leaf margin, bract length or form, size of flower, leaf or fruit, or degree 

 of pubescence which may or may not merit varietal rank. Most of these 

 preceding differences between mainland and island plants are due ap- 

 parently to long isolation on the islands affected by some genetic vari- 

 ation ; or to environmental differences of soil, humidity, or temperature ; 

 or possibly to longer intervals between devastating fires, floods, or other 

 catastrophic agencies. 



Endemism 



A study of the insular endemics is necessary for a just conception of 

 the island flora, its composition, its phylogeny, and its phytogeography. 

 The term endemics as used here relates to species, sub species, varieties, 

 or distinctive forms which are found only on the islands or, in some 

 cases, locally on the adjacent mainland. Preceding sections indicate the 

 nature of the insular isolation and some of the factors of the environ- 

 ment which have brought about large amounts of endemism for such 

 a limited area, probably intensified by the effects of genetic variation 

 in isolated environment. A typical example of this variation, with its 

 associated endemism is Lotus argophyllus. 



Descriptive Key for 

 Lotus argophyllus 



Calyx teeth as long as the tube. 



Stems woody, branches stocky with short nodes, silvery-canescent. 

 L. argophyllus niveus Ottley. 

 Santa Cruz Island. 

 Stems herbaceous. 



Umbels approximate at the ends of the branches, blade of banner 

 shorter than claw, silvery canescent. 



L. argophyllus Fremontii Ottley. 

 Sierra Nevada Mountains. 

 Umbels scattered along branches, blade of banner exceeding claw, 

 silky canescent. 



