n. UNCERTAINTY OF SPECIES. 35 



it, should always bear in mind that it consists not in the 

 technical description of specimens, but in the due appre- 

 ciation of species and afiinities ; that he who demon- 

 strates a fact such as the specific identity of two plants 

 hitherto believed to be distinct, or the affinities of an ob- 

 scure vegetable, renders a far greater service to science 

 than he who discovers, describes, or invents any number 

 of supposed species." (Edinburgh Review, October, 

 1856.) 



3. Uncertainty of Species. 



Of the species described in systematic works probably 

 not one in a hundred, perhaps not one in a thousand, has 

 ever been subjected to any crucial test of its distinctness 

 and permanence ; for instance, that of sufficiently re- 

 peated reproduction through seeds, under circumstances 

 well adapted for trying its constancy. Numbers of them 

 have been originall}" named and described from very few 

 individual specimens, brought home by travellers, who 

 likely never looked for intermediate and connecting 

 varieties, and seldom attempted to raise them afresh 

 from seeds, through a series of descents, either at home 

 or in the native lands of the presumed species. It is not 

 a very rare practice, indeed, to found species upon a soli- 

 tary specimen or two, or even upon a single fragment of 

 a plant ; so that difference from other plants, whether 

 slight or strong, is thus practically made the sole crite- 

 rion of a species ; and without ascertaining whether its 

 differences will prove casual or permanent. 



When specimens are collected in distant countries, 

 and brought home for description, the arrangement of 

 them into species must unavoidably be done in accord- 

 ance with, the resemblances or differences between few 



