Another example of the effect that a pecuUar soil type may 

 have on the distribution of a plant species is seen in the distribu- 

 tion of lone MsLnzsinitSi, Arctostaphylos myrtifolia (Ericaceae, 

 Plate ID). This small shrub is restricted to the lone formation, 

 which is a highly acid soil that is a mixture of clay, sand, and 

 ironstone. The lone formation occurs in a small area in the vicin- 

 ity of lone, Amador County, about 40 miles (64.4 km) southeast 

 of Sacramento. Another endemic of the lone formation is the 

 lone Wild Buckwheat, £'nogc»«i/m apricum (Polygonaceae). The 

 ecological reasons behind the restriction of these two plant species 

 to the lone formation are not clear, but they nevertheless provide 

 another example of endemism that is related to soil type. 



A rather peculiar example of endemism to another soil condi- 

 tion comes from the goldfield genus Lasthenia (Compositae). 

 Many species of this genus form large and colorful populations 

 in the valley regions of mainland California. However, L. minor 

 subsp. maritima is restricted to the guano-rich soils of offshore 

 islands, ranging from the Farallon Islands west of San Francisco 

 northward to some islets at the northern tip of Vancouver 

 Island (Plate 4C). So far as is known, this subspecies grows only 

 on nitrate-rich seabird guano. Tests of its foUage indicate that 

 this plant is a nitrate-accumulator, which suggests that it is able 

 to tolerate the high concentration of nitrates in soils that are 

 toxic to most other plants. It is probable that the distribution of 

 this subspecies is aided by the migration or casual flights of sea 

 birds from island to island along the Pacific coast. In cultivation, 

 L. minor subsp. maritima grows well on normal garden soil, but 

 in the field it seems unable to compete with other plant species 

 on any substrate but the highly friable and malodorous seabird 

 guano. 



The serpentine investigations of Kruckeberg, Walker, and 

 others, plus the investigations of a number of other biologists 

 and soil scientists, suggest the following general conclusions con- 

 cerning plants and soils: 



1 . Where soil patterns are complex, the vegetation patterns 

 are correspondingly complex. 



31 



