76 THE AMERICAN BOTANIST. 



two species as they grow in field or garden has no difficulty in 

 distinguishing them. The new species is well characterized by 

 its lighter green leaves, greater height, less compact flower- 

 clusters, restricted habitat and above all by its pale flowers and 

 later and longer season of bloom. Argillacea does not begin 

 to bloom until some time after pilosa has passed its prime and 

 when in full bloom no flowers of pilosa are to be found. The 

 height of its blooming season is the season at which the first 

 blooms of glaherrima unfold. Argillacea averages nearly 

 twice as tall as pilosa and generally forms more compact 

 clumps sending up a succession of flowering stems. One of the 

 most singular circumstances connected with its distribution is 

 the fact that while many roads and railroads lead from its 

 habitat across the prairie, argillacea declines to venture along 

 them while pilosa is abundant throughout. It is evident that 

 the descriptions of pilosa in the manuals have been drawn to 

 cover these two forms but there is too great a difference in 

 their time of blooming, color, size and habitat to admit of the 

 two being grouped as one species. For some time the plant 

 has been under observation in the garden growing close beside 

 pilosa and in the same kind of soil and under similar treatment 

 shows no tendency to intergrade with it. Albino forms of 

 pilosa, which bloom at the same time as the normal plant and 

 have the same general appearance have also been under culti- 

 vation by us and in no way resemble the new plant except in 

 the lighter color of the flowers. The albino flowers of pilosa 

 are, in fact, pure white, while argillacea appears to always be 

 lilac-tinged, at least as regards the tube of the corolla. 



