204 TORTULACE/E. 



areolation hyaline and rectangular, upper small, almost always 

 opaque and papillose. Fruit small, cleistocarpous, gymnostomous 

 or peristomate, peristome when present of 16 short, more or less 

 imperfect, entire or bipartite teeth, erect. 



I have followed Lindberg and Braithwaite in uniting under 

 one genus the species variously ranged under Systegium, 

 Hymenostomum, Gymnostomum, Weisia, and Eucladium ; but 

 have separated under Trichostomum the more robust, distinct 

 species usually placed under that genus, which have a very 

 different facies, and for the most part a more highly developed 

 capsule and peristome ; while in the present genus there are few 

 or none among the European species at least, except W. vertic- 

 illata, with the peristome at all well-developed. 



The name Mollia (used by Lindberg and Braithwaite for this 

 genus) must be rejected, as pointed out by Le Jobs (Rev. Bry., 

 1895, p. 19), since it was employed in 1824 by Martius for a genus 

 of Tiliaceae, for which genus it has been generally adopted and 

 has been in use ever since. 



{Capsule immersed, lid very minute, persistent 2 

 Capsule exserted ; lid larger, deciduous 4 



{Leaf-margin strongly involute above 1. crispa 

 Leaf-margin plane above 3 



/Perichsetial Is. long, erect; leaves crisped when dry .*. multicapsularis 



3\Perich£etialls. few, short, divergent; Is. scarcely crisped 3. Mittenii 



{Leaf-margin strongly incurved above 5 

 Margin plane or recurved above 7 



("Plant little branched ; Is. narrow, twisted when dry 6 



^\Plant much branched ; Is. wider, incurved when dry (gymnostomous) ...7. tortilis 



, /Peristome present 8. viridula 



\ Peristome absent 6. microstoma 



/Leaves toothed below, entire above ; plant glaucous - 14. varticillata 



' \ Leaves entire, or crenulate merely with projecting cell-walls 8 



„/ Nerve distinctly excurrent 9 



\Nerve vanishing in or below apex II 



/Capsule scarcely exserted, seta about i-line long 4. rostellata 



"\Capsule well exserted on longer seta 10 



{Stem decumbent below ; Is. squarrose ; peristome absent .J. squarrosa 

 Stem erect ; peristome present 9. mucronaia 



{Stem very short; Is. Ungulate, obtuse 12 

 Stem usually longer ; Is. more or less acute or subacute 13 



/Basal cells of leaves very long and narrow 10. tenuis 



\ Basal cells short //. calcarea 



/Upper cells minute, opaque ; nerve thick 12. rupestris 



^ \ Upper cells clear and pellucid ; nerve slender 13. curvirostris 



A. SYSTEGIUM. 

 Capsules immersed, cleistocarpous ; plants very small. 



