ECOLOGY. 365 



1873 and 1893-1895. The series of dry years exhausted the hope and 

 the credit of the newcomers, and their ranches were sold to the stock- 

 men or simplj^ abandoned. This process can only be repeated as a 

 consequence of future droughts, until the West recognizes that much 

 of its area can never be used profitably for any purpose except that of 

 stock-raising. This realization can hardlj^ come until repeated failures 

 at dry-farming have demonstrated that extensive regions can never 

 be used for crop production. These areas can be determined with 

 much accuracy at present, both by means of the indicator vegetation 

 and by means of crop failure and the abandonment of farms. This is 

 especially true when the rainfall record is taken into account. All of 

 this is of little avail, however, until the State recognizes that settle- 

 ment is one of its important functions, and that it can not be left 

 to political immigration bureaus or to unscrupulous real-estate dealers. 

 When it does recognize this, the settlement of the State's lands will 

 be put into the hands of the experiment stations, or of scientific com- 

 missions, such as that of California. Only when this is done will the 

 settler be able to make an adequate home and the State to profit by 

 his production. 



Ruhher Plants, by H. M. Hall and Frances Long. 



During the past three years, about 340 sets of specimens, repre- 

 senting 250 species, have been assembled from all parts of the West 

 and subjected to chemical examination for rubber. The results show 

 that rubber occurs in a much larger number of species tlian heretofore 

 supposed and that the amount present in some of them is sufficiently 

 great to justify experiments looking toward their cultivation on a 

 commercial scale. At any rate, the results thus far obtained, and 

 especially the chemical examination of this large number of native 

 plants, Vv'ill be of definite scientific value. Furthennore, they serve to 

 indicate the species and forms which are most likely to yield results of 

 commercial importance if follov*'ed up on a large scale. Several kinds 

 of milkweeds of the genus Asclepias are the most promising for further 

 study. "WTiile earlier examinations by rubber chemists indicated 

 about 2 per cent as the maximum rubber content of these plants, it is 

 now established that as high as 8 per cent of rubber may be obtained 

 from the leaves by the selection of proper species and ecologic forms. 

 In one leafless desert-species the i-ubber content is about 5 per cent of 

 the entire plant. 



It is reasonably certain that the iiibber content of milkweeds can 

 be considerably increased through breeding and selection. Since some 

 of them grow readily on poor soils unsuited to agricultural crops, it is 

 not beyond the range of possibility that they maj^ in time constitute 

 an important crop of the arid West. For this reason, some attention 

 has been given to the conditions of growth and the formation of rubber 



