660 PROCEEDINGS OF THE ACADEMY OF [Oct., 



such conditions are likely to have a very marked effect in producing 

 local forms from widely distributed species, while, on the other hand, 

 a freely moving animal is either not so easily affected or simply avoids 

 localities within its range where soil conditions, etc., are uncon- 

 genial. Thus the pine-barren region of southern New Jersey, where 

 soil conditions differ totally from the lower Delaware valley, though 

 in the same life-zone, presents a most distinctive flora, but not a single 

 "subspecies" of bird or mammal has been differentiated from those 

 found in the latter area. Such species as are not averse to the con- 

 ditions there presented occur unchanged, while others simply avoid 

 the region and are conspicuous by their absence. Some very local 

 races of mammals have been differentiated, it is true, in the Dismal 

 Swamp of Virginia and other similar spots, but the effect of purely 

 local conditions upon plant life is vastly greater than upon animals. 



My studies have been entirely too limited to warrant any attempt 

 to account for the origin of these local plant races, even in the genus to 

 which I have devoted especial attention, but the point that I would 

 particularly emphasize is that we have in these forms, which grow often 

 side by side, just as clearly differentiated races as the geographic sub- 

 species of vertebrates, and that they can be designated by trinomials 

 to better advantage than by the binomial method now generally in 

 vogue, even though the grouping be admittedly arbitrary in some 

 instances (cf. Condor, 1903, p. 43). The careless use of the trinomial or 

 varietal name in botany for all sorts of variation, purely individual, 

 albinistic, etc., of course acts as a prejudice against applying it to w^ell- 

 established racial forms of this kind, but with the tremendous increase 

 in species that we have recently witnessed in some genera the benefits 

 of the trinomial system should be apparent. Unless we are thoroughly 

 famihar with a genus, it is impossible to tell in a strictly binomial sys- 

 tem which forms are clearly defined species and which are slightly 

 differentiated races of a well-known type, while the use of trinomials 

 indicates this at a glance. 



Of course, in either animals or plants there must be some limit to 

 the number of forms recognized, and nomenclature becomes absurd 

 when applied to variants which can only be recognized by, perhaps, 

 one or two specialists who have devotee years to the study of the group. 

 This limit would seem to have been passed in the genus Cratcegns. 

 While there are admittedly a large number of species in eastern 

 North America, the two hundred or more that have been proposed seem 

 to more than cover the ground, especially since I have seen sets of 

 specimens collected from six bushes and submitted to three leading 



