616 THE AMERICAN NATURALIST [Vol. XLV 



Trelease, 17 in a recent paper on his favorite agaves, 

 says : "... my own conception of specific identities and 

 differences in the genus oscillates as my study pro- 

 ceeds. ..." 



While ultimately work of this nature, conscientiously 

 carried out, leads to a clear delineation of the characters 

 peculiar to each species, subspecies, variety, etc., there is 

 reached, usually not so very long after the inception of 

 the work and very long before its termination, a period 

 of chaos which, to say the least, is the reverse of stimu- 

 lating and ordinarily sufficient to dampen the ardor of 

 the greatest enthusiast. Thus, in my cultures of local 

 forms of Capsella Bursa-pastoris, the four forms 

 described by S hull 1 8 and some of those of Almquist 19 

 can be recognized readily. But there remain so many 

 whose classification is doubtful at the present time that 

 it would cause Mr. Murdock, associated with me in this 

 investigation, and myself to throw up our hands in 

 despair, were it not for the fact that there have appeared 

 in our cultures extreme forms, so striking and so 

 different from any previously described, that we are in- 

 clined to believe we are possibly dealing with mutations 

 in the sense of de Vries (Fig. 1). Research along these 

 lines requires long and tedious experimental efforts. It 

 is a different matter where the finding of distinctly new 

 forms in an old territory is concerned. Here an element 

 of chance largely enters. By increasing the number of 

 our observations our chances of discovering something 

 new may be increased materially. In other words, 

 directly or vicariously a large amount of ground has 

 to be covered. Yet I am not satisfied that a thorough 

 knowledge of a comparatively small area would not lead 

 to equally satisfactory results. The one requires about 

 as much exertion as does the other and certainly the 



"Trelease, W., "Species in Agave," Proc. Amcr. Phil. Soc, 49: 232, 

 pi. 32, 33, 1910. 



"Shull, G. EL, "Bursa Bursa-pastoris and Bursa Heegeri Biotypes and 

 Hybrids," Cam. Inst. Publ., No. 112, 1909. 



" Almquist, E., "Studien ueber die Capsella Bursa-pastoris (L.)," Acta 

 Eorti Berg., 4, No. 6, 1907. 



