Sierra Nevadan District. 621 
a close and fine sod. They abound throughout the alpine and subalpine 
belts of these mountains, 
The vegetation consists of species of Calamagrostis, Gentiana, Solidago, Ivesia, Orthocarpus, 
Pentstemon, Trifolium and masses of the genera Hypnum, Dieranum, Polytrichum, while mats of 
Salix glauca var. villosa, Bryanthus Breweri and Vaccinium caespitosum occur in such meadows 2). 
=}: i ormation is found aslant upon moraine covered hillsides, 
trending in the direction of greatest desclivity in the alpine and subalpine belts. e following 
genera of plants are represented: Lilium, Delphinium, Lupinus, Senecio, Allium, Castilleja, Mimulus, 
Pentstemon, Aquilegia, Silene, Wyethia, Erigeron, Phlox, Zauschneria, etc. Compare the alpine 
flora of this belt according to ENGLER?). 
ar lpine summit of Mount Rose above Truckee Valley in western Nevada is subject to 
winds of great velocity which in winter blow the snow out of the crevices of the rocks, so that 
many of the alpine species are exposed to extreme wintry conditions. The alpine belt begins 
with the prostrate form of Pinus albicaulis (10,000 feet) and here occur the arctie willow, Salix 
petrophila, Arabis depauperata, Arenaria Nuttallii, Castilleja ineonspicua, Cerastium Behringianum, 
Draba densifolia, Eriogonum rhodanthum, Festuca Kingii, Gilia montana, Oxyria digyna, Pentstemon 
Davidsonii, Phlox condensata, Poa longipedunculata, Polemonium montrosense, Raillardella nevaden- 
sis, Ribes Churchii, Senecio oceidentalis and Trisetum subspicatum var. m 
D. San Bernardino District. 
This phytogeographic district comprises that part of the California west of 
the Colorado and Mohave deserts and includes the San Bernardino and other 
ranges of mountains as also the coast plain south of a line which follows the 
Cuyama, or Santa Maria River and the Tehachapi range of mountains, or 
approximately that part of California, including the detached islands, south of 
the 35th degree of north latitude. Its southern boundary is marked by the 
Sonoran Desert Region. A sketch of the origin of the flora and its affınities 
has been given and a detailed statement with reference to the different floral 
elements is not necessary at this point (see ante p. 274). 
It has been thought expedient to deal with the island flora as distinct from 
that of the mainland. 
a) Insular Territories. 
The islands concerned in this sketch are San Miguel, Santa Rosa, 
Santa Cruz, Ana Capa, forming a northern group, and San Nicholas, 
Santa Barbara, Santa Catalina and San Clemente, forming a southern 
group. These islands are remarkable continental islands presenting in their 
flora many points of divergence from that of the adjacent mainland, for example, 
the absence of such prevailing genera as Ribes, Lupinus, Astragalus, Potentilla, 
Horkelia and in the presence of such genera as Lyonothamnus, Crossosoma 
and Zavatera absolutely peculiar to them. Such locally distributed mainland 
trees, as Pinus Torreyana, Malacothrix incana and Leptosyne gigantea are on 
the islands luxuriant and abundant. 
343. 
1) Sun, Cuartes H.: The wild Gardens of the Sierra, IX (1896): : 
5* 
2) Encrer, A.: Die pflanzengeographische Gliederung Nordamerikas, 
