Juncus niarginafiis and its Varidies. 127 



this paper have l)eeii taken from the hihels in the herharia of 

 Harvard University, Columljia College, the Missouri Botanical 

 Garden, and the Academy of Natural Sciences of Philadeli)hia, 

 the private herbaria of Mr. A\"illiam M. Canby and Captain John 

 Donnell Smith, and the National Herbarium. 



The disposition which is here made of the tyi)e form and 

 varieties of Jinicus marginatus may serve as a general illustration 

 of a method of dealing with species and varieties which is in 

 accord with our present knowledge of the evolution of species 

 and of the geographic relationship of these plants with each 

 other. The writer, having first secured a considerable amount 

 of material, separated the specimens into the three groups which 

 their examination naturally suggested. Next the names which 

 have been published for any one of these forms were taken up 

 and the original descriptions and the type specimens examined. 

 In some cases the t3''pes were not accessible, and under those 

 circumstances it was necessary to identify the plant either by 

 description alone or by the aid of collateral evidence. In this 

 manner it is believed that the earliest name applied to each of 

 these forms has been ascertained, one of them, as it proved, hav- 

 ing never before received a distinctive name. The next step was 

 to lu'ing together a still larger number of specimens, identifying 

 each one according to the facts already known, ascertaining the 

 localit}^ in which it was collected, and marking its position upon 

 a map. It was found that the type form of Jancus marf/inatus 

 merges by a full series of intergrades into Juncus marginatus 

 aristalatus, and that in the states of Nebraska and Kansas it seems 

 to intergrade also with Juncus marginatus setosus. The latter shows 

 a close relationship with the variety aristulatus, but, so far as indi- 

 cated by the specimens examined, does not fully intergrade with 

 it. The differences between these two, however, are so slight that 

 there is reason to expect the occurrence of intergrades. The 

 type form of Jancus marginatus ranges from Maine southward 

 through the Atlantic States to Florida, and occurs again at a 

 l)omt in the province of Ontario opposite Detroit. The variety 

 aristulatus ranges from New York city southward along the 

 coastal plains to Florida, westward through all the States 1>order- 

 ing the Gulf of Mexico, and northward, in the Mississippi valley, 

 in apparently isolated localities, to southern Michigan. South 

 of the United States it follows the eastern coast at least as 

 far as Cohan, Guatemala, and one specimen is reported to have 



