220 CALIFORNIA ACADEMY OF SCIENCES. 



flora and also somewhat the form and habit of the species. 



The distorted trees, the prostrate spreading bushes and 

 the encroaching sand dunes show plainly that the wind 

 most affecting the vegetation comes from the north and 

 northwest. 



Santa Cruz, on account of its easterly location, receives 

 more protection from the Santa Inez Mountains against the 

 north winds than Santa Rosa, and the high mountains of 

 the island itself aflbrd additional shelter to the plants and 

 trees of its valleys and cailons. Its large area, its sheltered 

 position and its physical characteristics account for the 

 large number of species growing upoii Santa Cruz Island. 



San Miguel, the westerly member of this group of islands, 

 is almost wholly unprotected by the mainland coast, and re- 

 ceives the full force of the north Avest winds. 



Santa Rosa, situated to the windward of Santa Cruz, and 

 consequently receiving less protection from the northern 

 coast, with its topography not so mountainous or so varied, 

 possesses a flora smaller in number of species, and as it 

 partakes somewhat of the conditions of both the adjoining 

 islands its flora is a mixture of that of those two islands; 

 the eastern side approaching nearly to the conditions of 

 Santa Cruz, its flora is mainly of species growing upon that 

 island, while the western side approaching San Miguel in 

 situation and physical characteristics resembles it in gen- 

 eral botanical features. The shrubby vegetation and trees 

 of Santa Rosa, are nearly all confined to the sheltered hill- 

 sides and canons of the eastern portion of the island. 



Many of the plants of the islands vary in their form and 

 habit more or less from those of the same species growing 

 upon the neighboring mainland, and those of one island of- 

 ten differ much from those of another, and even upon the 

 same island some species present a width of variation, tlie 

 extreme limits of which appear distinct. The species of 

 Santa Rosa, as would be expected from the conditions of 

 their existence, vary not only from those of the mainland 



