346 CARNEGIE INSTITUTION OF WASHINGTON. 



rootstocks, when the change to the sun-form became complete. In all 

 of these cases, herbarium specimens of the leafy shoots were taken when 

 the transplants were made or before the canopy was removed, and 

 again from the same rootstocks after the change had occurred. These 

 specimens serve for direct comparison and furnish a definite record of 

 the changes produced. 



Although some characters are easily modified, others prove to be 

 much less plastic. This applies even to such a variable as stature, 

 at least when this is coupled with other characters. The alpine variety 

 of Solidago humilis retains its depressed habit during its first growing 

 season after being transplanted to 8,000 feet, where its reciprocal at- 

 tains a stature of 1 to 3 feet. Similarly, Zygadenus alpinus retains its 

 alpine habit and produces flowers when only 2 to 3 inches high, even 

 when grown alongside of its reciprocal, typical Z. elegans, which is 1 to 

 2 feet tall. It is possible that these alpine forms will become con- 

 siderably modified under the cumulative effect of the new environment 

 in the course of several years, but there is at present no evident tendency 

 towards such modification. 



Taxonojyiic Monographs, by F. E, Clements and H. M. Hall. 



The preparation of detailed monographs of three important genera 

 of North American plants, Artemisia, Chrysothamnus, and Atriplex, 

 is now nearing completion. Field work has been carried on in all of 

 the western States to determine the extent of variation within the spe- 

 cies, and the value of the criterLa used in their classification. An exami- 

 nation of tjTDe-specimens and other authentic material has been made in 

 most of the principal herbaria in the United States, and many forms 

 have been subjected to experimental tests in the gardens on Pike's 

 Peak and at Berkeley. Quantitative methods have been used so far as 

 possible and extensive series of counts and measurements have been 

 made, especially of flowers and fruits. The results have thrown much 

 light upon the value of the criteria commonly used, and in some 

 instances have disclosed important differences. By the use of quan- 

 titative and statistical methods, it has been found that great inequality 

 exists between the taxonomic groups heretofore accepted. Many so- 

 called species are based upon fluctuating characters of little value, 

 while other forms are more sharply set off from their neighbors than has 

 been supposed. A new alinement has become necessary to bring the 

 forms into a sequence that expresses their natural relationship. 



Phylogeny has been taken as the key-note in the preparation of these 

 monographs and an efl'ort has been made to present the relationships 

 of the numerous forms in a readily intelligible manner. This is done 

 by a series of diagrams so devised that the authors' conception of 

 phylogcnetic origin and relationship between any two varieties may 

 be readily seen. The distinctive characters of each taxonomic unit, 

 whether variety, species, or section, are also indicated on the diagram. 



