ECOLOGY. 399 



(4) plot tests of yield under varying conditions and in different 

 localities ; (5) detailed study of the product and its uses in connection 

 with other rubbers; (6) by-products; (7) histological and micro- 

 chemical studies of the formation of rubber in plant tissues. In addi- 

 tion to the latex plants, these investigations will include such shrubs 

 as Chrysothamnus, which yields the rubber chrysil, and guayule, a 

 Mexican shrub now grown in Arizona and California. 



AiTangements have been made by which both rubber and paper will 

 be manufactured from these plants in sufficient quantity to permit of 

 thorough tests as to quality, properties, and uses, as well as the yield 

 under ordinary commercial processes. Suitable tracts for experimen- 

 tal planting have been offered at several places in the West, as well 

 as stations for breeding and other experiments, and these are being 

 utilized as rapidly as opportunity permits. 



Origin and Nature of Laticiferous Tissue, by Frances Long. 



In connection with the studies on rubber plants an extensive in- 

 vestigation has been begun of the histology and chemistry of latici- 

 ferous tissue in various groups, such as Euphorbiacece, Asclepiadaceoe, 

 Cichorieoe, etc. Material has been collected in nature of most of the 

 latex-bearing genera of the West, and particular attention has been paid 

 to obtaining the same species in different conditions and at different 

 times. In addition, latex plants have been grow^n in garden and green- 

 house, partly for the purpose of obtaining milk-tissue at all stages of 

 development and partly to permit the manipulatioQ of water-content 

 and light. The primary objective of the study is to determine the 

 variations in the amount of latex and its rubber-content, and to 

 relate these to the physical factors and the growth of the plant. 



Root Development and Absorption in Crop Plants, by J. E. Weaver, F. C. Jean, 



and J. W. Crist. 



Life-history studies of root development have been m^ade at three 

 or more periods in the growth of crops at Peru and Lincoln (Nebraska), 

 Phillipsburg (Kansas), and Burlington (Colorado). In most cases 

 the descriptions of extent and position of roots were supplemented 

 by drawings made in the field as the roots were excavated. The ex- 

 periments were repeated the follo^\'ing season, and the variations in 

 root-habit recorded and correlated with the physical conditions. 



The crop yield was determined in terms of grain, tubers, forage, or 

 total dry weight. The smaller cereals were harvested from repre- 

 sentative meter-quadrats of each species plat, the plants thoroughly 

 air-dried and finally weighed. The yield of above-ground parts 

 generally stood in direct relation to the water-content of the soil, 

 being least at Burlington, intermediate at Phillipsburg, and greatest 

 at Lincoln. Thus, the average yield of dry matter by oats, cut in the 

 dough stage, was 180, 366, and 792 grams per square meter for the 

 respective stations. 



