A. Gray— Flora of Worth America. 329 



may fairly conclude that if the work had been pushed on to 

 completion, say in the year 1850, the 3076 species of Pursh's 

 Flora in the year 1814 might have been just about doubled. 

 Probably more rather than less ; for if we reckon from the 

 number of the Composite, and on the estimate that they consti- 

 tute one-eighth of the phaenogamous plants of North America, 

 instead of 6150, there would have been 8430 species known in 

 the year specified. 



It most concerns us to know the number of species which, 

 after the lapse of thirty years more — years in which exploration 

 lias been active, and has left no considerable part of our great 

 area wholly unvisited— the now revived Flora has to deal with. 

 ^ e ran make an estimate which cannot be far wrong. In the 

 y/n I s 78, my colleague, Mr. Watson, finished and published 

 his Bibliographical Index to the Poljpetalse of Morth America, 

 covering, that is, the same ground as the first volume of Torrey 

 and <i rav's Flora, completed in 1840. In it the 2200 species of 

 tlie latter date are increased to 3038. The "Gamopeialce after 

 Damp site" in the Synoptical Flora, brought out in the same 

 year, col i tains 1056 species. The two together must make up 

 ■'';'' "f our phaenogamous botany, that is. adding the increase 

 °t' the last four years, about 5000 species. And so Mr. Watson 

 •id"i»rs the estimate of 10,000 species for our known Phamogams 

 and Ferns. My impression is that the species of Composite 

 have increased at a rate which, unless they exceed the eighth 



The number of introduced species of various orders, which will 

 have to be enumerated and most of them described, is, unhap- 

 l"!y. fast increasing;* and new indigenous species are almost 

 daily coming to us from some part or other of our wide terri- 

 tory. So that the 10,000 species of this estimate may before 

 long rise to eleven or twelve thousand. Only the experienced 

 ^tamst ean forma just idea of what is involved in the accurate 

 'i^'t'iinination and proper coordination of 10-12000 species, 

 and in the putting of the results into the language and form 

 which may make our knowledge available to learners or to 

 succeeding botanists. 



Moreover, there is of late an embarras des richesses which is 



- rious as respects labor and time. The continued 



and ever increasing influx of materials to Cambridge, beneficial 



as it ever is, is accountable for this retardation of progress in a 



greater degree than almost any one would suppose. The her- 



• ho.,, materials" this work is mainly done, and 



- ■ n, like the Temole. full forty and six years in 



b uddmg, has received the contributions of two generations of 



* I say " iml: lt ,, the natural character of our flora, and 



- .. . .. i 



K've to these denizens the rights of adopted citizens. 



