INTRODUCTION. 



IX 



covered "by examining all the parts. in a combined or complicated fcene. 

 And when a plant is difcovered, concerning which we are doubtful whe- 

 ther it is a fpecies of itfelf, or only a variety of fpecies already known, 

 we ought carefully to collate it with the original, from which we fuppofe 

 it may pollibly be derived ; and if we find it to agree in the'number, fi- 

 gure, and lituation of its parts, and that the matter of which it is com- 

 pofed, agree in fubftance or texture, we may reafonably fuppofe, that the 

 doubtful plant is a variety and not a fpecies, though it may be much dif- ' 

 ferent, in refpecl to time, foil, magnitude, colour, Sec. 



On the contrary, though two plants may agree in colour, time, foil, 

 fituation, fize, fmell, tafte, &c. yet if they diftgree in any one effential 

 mark, we are neverthelefs certain of their fpecific diftinction. For in- 

 ftance, fuppofe the Agaricus fimitarius has an upright white ftem, grow- 

 ing from a bulbous root, which is deftitute of volvaj fo has the Agaricus 

 annulatus. Suppofe it further, to have a large white pileus, brown at the 

 apex, and covered here and there with foft brown fcales ; fuppofe it to 

 have a white curtain, and gills of a pale flefh colour, while young, and 

 changing their colour afterwards ; the Agaricus annulatus exhibits all the 

 above characters, as evidently as the other. Thus far, therefore, no cer- 

 tain fpecific mark is difcoverable ; but on examining them a little further 

 we find, that the gills of the jimetarius are arranged in one feries only, 

 being all of equal length, and extended from the rim of the pileus to the 

 top of -the ftem; but in the annulatus they are arranged in feveral feries, 

 unequal in length, which is a certain mark of diftinction in the two 

 fpecies. This one dingnoftic being found, we then fupport it by aids, 

 drawn from habit, figure, foil, fize, duration, fmell, tafte, colour, and 

 diffolution; all which being properly attended to, will, with the affiftance 

 of application to the ftudy, and actual obfervation made upon the plants in 

 the different ftages of growth, > render the knowledge of their fpecific dif- 

 tinctions, both eafy and certain. 



To explain a little further what I mean, by aids to fupport the fpecific 

 mark, in the above inftance, The pileus in the Agaricus fimitarius, is of 



b an 



