The Primitive Mosses 



There are sixty-four species in all, two in the United States. 



Trematodon ambiguum, Hornsch. 



Habit and habitat. Wet sandy places on hills ; in peat-bogs, 

 ditches, etc., of Alpine regions. 



Name. The specific name ambiguum, doubtful, was given to 

 this species at the time it was classified in the genus Dicranum 

 (1792) and expressed the doubt as to its rightful position, which 

 was determined in 1803. 



Plants (gametophyte) . Short, | to I inch long. 



Leaves. Open, lance-shaped, channelled ; apex long and 

 slender ; base concave, oval-oblong ; margins entire, inrolled ; 

 vein extending beyond the leaf-blade (excurrent). 



Leaves at the base of the pedicel. Large, oblong, 

 with a short tapering point. Perichaetial leaves. 



Plant stripped of 

 leaves to show two 

 male and one fe- 

 male cluster. 



Tooth. 



Spore-case with 



veil. Lid. 



T. anibiguum. 



Vertical section of peristome 

 showing two cells of the annulus 

 at the base of a single tooth. 



Habit of flowering. Male and female flowers in different places 

 on the same plant (autoicous) ; male flowers terminal on a basal 

 branch, bracts small, taper-pointed. 



Veil (calyptra). Translucent, slit on one side (cucullate). 



Spore-case. Oblong, straw-coloured or orange-brown ; in 

 length equal to or shorter than the slightly arched neck (collum) 

 which is swollen on one side at the base. 



Pedicel (seta) .Long, twisted, to i inches long, straw- 

 coloured. 



Lid (operculum). Conical at the base; beak, long and oblique. 



149 



