162 TORTULACE^. 



Order IX. TORTULACEyE. 



Mosses of usually low growth, radiculose only at base. 

 Leaves variable, from linear to spathulate ; areolation usually 

 thin-walled and hyaline at base, often small, obscure and papillose 

 above. Seta straight, capsule erect or very slightly inclined, 

 oval, oblong or cylindrical, calyptra usually narrow and cucullate, 

 peristome none or single, of 16 straight or spirally twisted teeth, 

 entire or divided, often into 32 filiform branches, papillose. 



A large and polymorphous Order, very difficult to define, 

 owing to the number of lowly organised forms which, while 

 widely differing from the normal type of the Order, are clearly 

 inseparable from it by reason of the regular gradation between 

 them and the higher species. The structure of the leaves is more 

 important, perhaps unusually so, than that of the peristome, 

 which exhibits considerable variation even within the same genus, 

 and is indeed often absent from species whose close relationship 

 with other highly peristomate ones is undoubted. On one side 

 Tortulaceae comes very near to Dicranaceae, especially through 

 Ceratodon ; on another it approaches Funariacese ; the higher 

 species of Tortula show great affinity to Encalypta, while 

 Cinclidotus is related to Grimmiaceas, and other relationships 

 could be pointed out; in a linear arrangement it is impossible to 

 preserve these affinities unbroken, and we are obliged to be 

 contented with drawing attention to the more important of them. 

 With some slight variation I have for the most part followed 

 Lindberg's generic divisions and arrangement. I have however 

 united Ephemerum with the Funariaceae, as despite their near 

 resemblance to Acaulon they appear to be quite as closely related, 

 through Physcomitrella, with that Order, and the areolation is 

 rather Funarioid than Pottioid. 



Tribe 1. Potties. 



Leaves broad in outline, in only a few species narrowly 

 lanceolate ; peristome when present of 16 or 32 teeth, entire or 

 cleft, sometimes to base, straight or twisted, often united at base 

 into a tube. Upper cells more or less hexagonal, lax and pellucid 

 or smaller and obscure. 



36. ACAULON CM. 



Plants minute, bulbiform. Upper leaves very much larger, 

 concave, convolute. Capsule spherical, almost or entirely without 



