66 Mr, Menzie s V Arrangement of the 



trlchum commune, page 229, the author makes the following obfer* 

 vation : 



" Polytrkhum hoc calyptra gaudet duplki: exterior e pilofd t inter tore 

 multo minor e, membranaced, albidd, lavi\ exteriore obteftd." 



^ I do not find that Leers made any pra&ical application of this 

 difcovery, or traced it in any other fpecies : but Mr. Curtis, a va- 

 luable member of this Society, who made the fame difcovery the 

 year following, purfued it further, and finding the double calyptra 

 conftant in other fpecies as well as the Polytrkhum commune^ he ap- 

 plied it, with his ufual perfpicuity and difcernment, as a difting mill- 

 ing character of the genus, in one of the numbers of his Flora 

 Londinenfts, published in the year 1778; and I am confident that 

 a more beautiful or a more obvious one could not be fele&ed, hav- 

 ing found it conftant and invariable in every fpecies here deicribed 

 except the Polytrkhum magellanicum, which has only a fingle frnooth 

 calyptra; but then it fo ftrongly pofTeffes the peculiar habits* and 

 every other characleriftic of the genus, that I think it cannot pof- 

 fibly be feparated. I have therefore drawn up the following general 

 eharaaer, which, with the above exception, will be found appli- 

 cable to every individual of this natural family. 



POLYTRICHUM. 



i Natural Character* 



THE plants of this genus, whether fingle or branched, grow 

 moftly erecl: from the ground, and have an unpliant ftiffnefs or ri- 

 gidity of appearance that peculiarly diflinguiikes them from mod 

 others of this natural order. 



3 The 



