176 Dr. Smith'j Obfervations on 



of acquiring an entirely new fmell, either by accidental variation of 

 foil, a dry fituation, or fome change in their conftitution which we 

 cannot underftand. Thus the fmcll of Sweet Bafil, Ocymum, is ac- 

 quired by fome, that of Orange by others, and one or two acquire a 

 peculiarly fwcet fmell, which belongs alio to a fweet variety of the 

 Garden Thyme, Thymus vulgaris, called in Norfolk, where it is very 

 common, Frankincenfe Thyme. The fmell and tafte of Pepper 

 Mint, which feem natural to our well-known fpecies fo named, 

 are ftiared in common with it by fome others, even wild in Eng- 

 land ; and the Mentha piperita ufcd in Sweden, and defcribed by 

 Linnaeus and Bergius, is certainly a different fpecies from ours. 

 Indeed I am told by thofe who cultivate our Pepper-mint for medi- 

 cal purpofes, that, to keep up its quality, the roots muft be tranf- 

 planted every three years ; otherwife it degenerates into the flavour 

 of Spear-mint, from which neverthelefs it is fpecifically different. 



The fhape of the leaves, though in fome inftances tolerably con- 

 ftant, in others is found very variable both as to length and breadth. 

 This is particularly the cafe in the fpiked Mints. The degree of 

 hairinefs of the leaves, and in general of the whole plant, is ex- 

 tremely uncertain. I need fcarcely fay, colour is not at all to be 

 depended on. Many mints expofed to much air and fun become 

 altoo-ether purple. The length of the ftamina is alfo a variable cir- 

 eumftance. As all thefe plants have creeping roots, the feeds are 

 jarely perfeftcd, and even the ftamina frequently prove abortive. 

 In this cafe they are commonly tliorter than the corolla. 



The inflorefcenre in this and every genus has been confidered by 

 all authors as affording indubitable marks of fpecific diftindlion. 

 The mints have been divided into fpiked, capitate and verticillate. 

 Some very ftriking circumftances have led me to doubt whether even 

 thefe diftin. lions are well founded. I am very confident the fame 

 Q fpecies 



