The Primitive Mosses 



Veil (calyptra). Split up one side. 



Spore-case. Bright orange, symmetrical. 



Pedicel (seta). Shorter than the spore-case. 



Lid (operculum). Short, conical. 



Teeth (peristome). None. 



Spores. Bright, rusty brown, mature in autumn. 



Distribution. North America. 



Genus GYMNOSTOMUM, Hedw. 



The species of the Genus Gymnostomum are found in 

 matted tufts on the ground and on limestone walls and rocks. 



The plants have slender stems branching 

 twice or many times to form clusters, with 

 terminal erect spore-cases, cylindrical or globose, 

 exserted on erect pedicels. 



The leaves are small, generally larger upwards 

 and tufted at the apex of the stem ; they are 

 lance-shaped with a solid vein prominent on 

 the back. 



The lid is long-beaked and falls to permit the 

 escape of the spores. There are no teeth, a 

 character which suggests the generic 

 name, from the Greek 7v/m>9, naked, 

 and a-rd/jia, a mouth. 



There are fifty-five species in all, 

 eight of them known in North America. 



Gymnostomum calcareum, 

 Nees & Hornsch. 



Habit and habitat. Densely tufted, 

 bright-green above, rusty below ; on 

 shaded limestone rocks. 



Name. From calcarius, pertaining 

 to lime, a name suggested by the 

 plant's habit of depositing lime. 



Plants (gametophyte) . Stems J to 

 f of an inch long, covered with root- 

 lets. 



Leaves. The lower very small, 

 gradually or abruptly larger upward ; 

 slender lance-shaped ; apex blunt ; 



143 



Leaf and 

 cross -section 

 to show 

 prominent 

 vein. 



Gymnosiomum calcareum. 



