I06 BROOKLYN BOTANIC GARDEN MEMOIRS 



color to the many arguments that species originate very slowly, even al- 

 though conditions, apparently favorable for species segregation, such as the 

 undoubtedly severe environment at Montauk, are at hand.* It may 

 possibly be true also, that botanists who erect species concepts upon finer 

 lines than the current manuals, would see in the dwarf, stunted or wind- 

 wrenched specimens of the Montauk flora, a host of nascent species, in 

 which the present writer sees merely ecological variations, or response to 

 the local conditions there. A good illustration of this is the species that 

 occur both in the wooded kettleholes and out on the open downs. Luxuri- 

 ance in the one place and thwarted endeavor in the other to produce normal 

 growth are constantly met with in the flora of Montauk. 



The age of this flora, — it is, of course, all post-glacial,— cannot be fixed 

 definitely. In an attempt to fix the relative age of different floras by the 

 percentages of monocotyledons and dicotyledons,! Harper has shown that 

 the former vary between 28% and 32.3% of the total flora in the glaciated 

 region which he has studied. The percentage of monocotyledons at Mon- 

 tauk, also a glaciated region, but subject to invasion from the adjacent 

 coastal plain, is 30.9%. Present ideas of the relative antiquity of mono- 

 cotyledons may, however, put a different interpretation upon the proportion 

 of them in any flora. 



Another rather interesting feature of the plants of Montauk in relation 

 to the environment is the so-called generic coefficient of the flora. J In 

 brief this proposition is that in regions of diverse ecological conditions 

 there will be a relatively higher proportion of genera produced than in a 

 region of generally similar character. The plan has been tried for many 

 regions and everywhere the generic coefficient (the proportion of genera to 

 species in any given flora) is high where conditions are pretty uniform, 

 lower where the conditions are diverse. 



For the regions nearest Montauk, considering both introduced and native 

 species the generic coefficients are as follows: 



* This is in harmony with the statement of Professor M. L. Fernald at the recent meet- 

 ings of the Botanical Society of America. In his paper "The Antiquity of species as indi- 

 cated by Insular and Peninsular Floras of Eastern Canada" he postulates comparative 

 fixity of species over long periods of years — 25,000 years. 



t Harper, R. M. A statistical method for comparing the age of different floras. Tor- 

 reya 5: 207-211. 1905. 



t For an account of the details of this, first proposed by Professor Paul Jaccard, see 

 Bull. Soc. Vaudoise Sci. Nat. 37: 547-579. 1901. loc. cit. 44: 223-270. 1908. New 

 Phytologist 11: 37-50. 1912. Rev. Gen. Hot. 26: 1-47. 1914. Also a paper by Pro- 

 fessor J. W. Harshberger on "The diversity of ecologic conditions and its influence on the 

 richness of floras." Proc. Philadelphia Acad. Nat. Sci. 67: 419-425. 1915. 



