

CONTRIBUTIONS FROM THE ROCKY MOUNTAIN 



HERBARIUM. IV. 



AvEN Nelson. 



SOME CHENOPODIACEAE 



Probably the most characteristic plants of the great saline 

 plains of the West and the similar basins of the intermountain 

 country are the Chenopodiaceae. Some of the genera in this 

 family are known by name, at least, to most people. Such, for 

 example, are greasevvood, the salt-bushes, winter-fat, Russian- 

 thistle, etc. Many of the species in this family are of remark- 

 ably wide distribution. As they become better known it is 

 found that the range of some, once supposed to be quite circum- 

 scribed, is really quite extended. The strongly alkali-impreg- 

 nated areas are so inhospitable that most plants are unable to 

 occupy them, and nearly all the members of this family have in 

 some way become tolerant of such soils. So far as the effect 

 upon vegetation is concerned, all of the saline districts are essen- 

 tially the same, the differences in the soil being apparently one of 

 degree rather than of quality. This fact coupled with another, 

 that this family has little competition on this kind of soil, may 

 account in a measure for the unusually wide range of some of 

 the species. Of course the other factors of environment are 

 operative upon these plants as upon others, but they seem less 

 potent than the soil in producing specific variation. 



ATRIPLEX. 



The foregoing remarks have been suggested by a rather 

 extended study of certain species of Atriplex occurring within 

 the Rocky mountain region. Not satisfied w^ith the view 

 afforded by the specimens in the Rocky Mountain Herbarium, 

 the loan of another large collection was solicited.' Some notes 



" I wish to express my thanks to Dr. William Trelease, Director of the Missouri 

 Botanical Garden, for the privilege of examining all the specimens illustrating the 

 species considered in this paper which are contained in the Engelmann herbarium 

 and the general herbarium of the Garden. 



1902] 355 



