BOTAMCAL GAZETTE. 133 



My impression is that the species of ( 'ompositce have increased at a 

 rate which, unless they exceed the eighth part of our PhsBnogams, 

 will warrant a still higher estimate. The number of introduced 

 species of various orders, which will have to be enumerated and 

 most of them described, is, unhappily, last increasing*; and new in- 

 digenous specic/3 are almost daily coming to us from some part or 

 other of our wide territory. So that the 10,000 species of this esti- 

 mate may before long rise to eleven or twe've thousand. Only the 

 experienced botanist can form a just idea of what is involved in the 

 accurate discrimination and proper co-ordination of 10-12,000 

 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 be- 

 coming serious 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 ot progress in a greater degree 

 than almost any one would suppose. The herbarium, upon whose 

 materials this work is mainly done. and which has been, like the Tem- 

 ple,full forty and six years in building.has received the contributions 

 of two generations of botanists, and the Torrey herbarium goes 

 back one generation further. Still the number of American speci- 

 mens annually coining to it is greater than in most former years. 

 Apart from the mere selection and care of these, consider how in 

 other ways it affects the rate of progress of the Plora.The incoming 

 of additional specimens may at a glance settle doubts as to the 

 validity of a species; but new specimens are as apt to raise questions 

 as to settle them, more commonly they raise the question as to the 

 limitation and right definition of the species concerned, not rarely, 

 also, that of their validhy. When one has only single specimens 

 of related species, the case may seem clear and the definition easy. 

 The acquisition of a tew more, from a different region or other 

 conditions, almost always calls for some re-consideration, not rarely 

 for re-construction. People generally suppose that species, and 

 even genera,are like coin from the mint,or bank notes from the print- 

 ing press, each with its fixed marks and signature, which he that 

 runs may read,or the practiced eye infallibly determine. But in fact 

 species are judgments — judgments of variable value, and often very 

 fallible judgments, as we botanists well know. And genera are 

 more obviously judgments, and more and more liable to be effected 

 by new discoveries. J udgments formed, to-day — perhaps with full 

 confidence, perhaps with misgiving — may to-morrow, with the dis- 

 covery of new materials or the detection of some before unobserved 

 point ot structure, have to be weighed and decided anew. You see 



* I say "unhappily," for they adulterate the natural character of our flora, 

 and raise difficult questions as to how niueh of introduction and settlement 

 .should give to these denizens the rights of adopted citizens. 



