GENERA PLANT ARUM. 357 



than a general and superficial acquaintance with any other 

 department than the one to which he devotes himself. This 

 inevitable state of things has its disadvantages. The reasons 

 for it do not really apply to the Ferns and their allies, and it 

 was naturally expected, as it is much to be desired, that these 

 should enter into the present work. May we hope that this 

 still may be ? 



Some idea of the progressive enlargement of the field may 

 be had by a comparison of the number of genera characterized 

 in these successive works. The phaenogamous genera of 



Linnaeus, " Gen. PI.," ed. 1, a. d. 1737, were . . 887 



" ed. 6, a. d. 17G1, "... 1,189 



Jussieu, " . . . . a. d. 1789, "... 1,707 



Endlicher, " . . . . A. r>. 1813, " (about) 6,400 



Bentham&> K a. d. 1883, "... 7,585 



Hooker, ) 



If the last had been elaborated upon the scale of Endlicher, 

 or with the idea of genera which is still common if not preva- 

 lent, the number of genera would have amounted to at least 

 ten thousand. An estimate of the number of known species 

 of each genus and higher group has been made throughout 

 the work — a rough approximation only, mentioning first the 

 number in the books, and the number to which, in the opin- 

 ion of the authors, these may probably be reduced by bota- 

 nists who adhere to the Linnsean view of species ; from which 

 it appears that upon the very strictest estimate their number, 

 as now known to botanists, is at least 95,620. In round 

 numbers, it may fairly be said that about 100,000 species of 

 phamogamous plants are in the hands of botanists. The five 

 largest orders, as well for genera as for species, are the follow- 

 ing, and in this rank: Composite?, Leguminosce, Orchidece, Ru- 

 biacece, Graminem. The high standing of the Orchid family 

 in the list will be a surprise to many. Linnasus knew only a 

 hundred species ; five thousand is now a moderate estimate 

 — about half as many as there are of Composite^, which hold 

 to their proportion of one tenth of the whole. In both fam- 

 ilies every country and district is largely peculiar in its spe- 

 cies and types. The far greater prominence of Compositce 



