April 12, 1907] 



SCIENCE 



581 



and harvesting were discussed. Attention was 

 called to the great number of varieties exist- 

 ing in this region and to the characters by 

 which they are distinguished. A description 

 was given of the Oued Souf oases in eastern 

 Algeria and of the peculiar method of grow- 

 ing date palms there in ' sunken gardens ' 

 among high sand dunes. The efforts of the 

 Department of Agriculture to establish date 

 culture in the southwestern United States 

 were also discussed. 



The 426th meeting was held on February 23, 

 1907, with President Stejneger in the chair. 



Mr. 0. V. Piper presented a paper exten- 

 sively illustrated by lantern slides, on ' Some 

 Features in the Distribution of Life in the 

 Columbia Basin.' The Columbia Basin com- 

 prises practically all of Washington and Ore- 

 gon east of the Cascade Mountains and the 

 greater part of Idaho. This region is entirely 

 covered with the Columbia lava of an average 

 thickness of about 1,000 meters. The central 

 portion of the basin is the lowest, ranging 

 from 150 to 300 meters altitude, from which 

 it gradually rises in all directions to the sur- 

 rounding mountains. The Cascade Moun- 

 tains on the west, the Bitter-Root and Eocky 

 Mountains on the east as well as the Blue 

 Mountains, are inhabited mainly by boreal 

 plants and animals pushed southward during 

 the glacial period. The lowest part of the 

 basin is occupied by the upper Sonoran plants 

 and animals and the intermediate region by 

 arid transition forms. 



In studying the inhabitants of this region 

 statistically, it is found that, if plants of con- 

 tinental range be excluded amounting to about 

 30 per cent, of the whole, that the follow- 

 ing proportions appear. Of upper Sonoran 

 plants, 7 per cent, are of California origin, 

 64 per cent, of Great Basin origin and 29 per 

 cent, are endemic. Of the arid transition 

 plants 33 per cent, are of California origin, 

 26 per cent, of great basin and 31 per cent, 

 endemic. It will be noticed, on comparing 

 these figures, that Californian arid transition 

 species have much freer access to the region 

 than upper Sonoran species. Indeed, at the 

 present time the arid transition area is still 



continuous from California into the Columbia 

 Basin. This with the prevailing southwest 

 winds is probably the reason why these plants 

 dominate over those of Great Basin origin in 

 the Columbia Basin, though the latter appar- 

 ently have much easier access. In the Colum- 

 bia Basin the upper Sonoran life area is prac- 

 tically coextensive with the area where the 

 rainfall is 12 inches or less and the character- 

 istic plant is the common sage brush. 



A second point of interest in the distribu- 

 tion of plants in this region, is the relation 

 which exists between the plants of the Blue 

 Mountains, those of the northernmost part of 

 the Cascade Mountains and those of tke Siski- 

 you Mountains. These regions are composed 

 largely of granitic mountains and in each of 

 them there is a considerable number of pecul- 

 iar species. It was suggested that the ex- 

 planation of this was to be found in the fact 

 that the greater portion of the Cascade Moun- 

 tain region is volcanic in character and com- 

 paratively recent in origin. It is possible, 

 therefore, that the plant species peculiar to the 

 granitic regions either prefer granitic soils or 

 else through volcanic conditions have disap- 

 peared from the greater portion of the Cascade 

 Mountains. While neither of these explana- 

 tions is entirely satisfactory the fact of the 

 peculiar relations of their floras is very clear. 



Another striking feature mentioned by the 

 speaker was in regard to the islands in the 

 northern part of Puget Sound. These islands, 

 including the southwest extremity of the Van- 

 couver Island, lie in the lee of the Olympic 

 Mountains and have the lowest rainfall of 

 any of the country west of the Cascade Moun- 

 tains. The rainfall on these islands varies 

 from 19 to 31 inches, practically paralleling- 

 the conditions of the arid transition area east 

 of the Cascade Mountains. The Cascade 

 Mountain form at the present time is a per- 

 fect barrier for arid transition and upper 

 Sonoran plants. Nevertheless, in some way a 

 considerable number of such species have 

 found their way to this region of low rainfall 

 in the northern part of Puget Sound. Among- 

 these are Opuntia missouriensis, Juniperus 

 scopulorum, Platyspermum scapigerum, Zyga- 

 derms pamculatuSj Lupirmis microcarpus and 



