SYNOPSIS OF ORDERS AND GENERA. 57 



Genus 81. Tortula. — Veil with a long beak spirally fissured; 

 peristome of thirty-two twisted teeth, united by a tubular 

 short or elongated basal membrane. 



Genus 82. Trichostomum. — Veil cucullate, smooth; peri- 

 stome of thirty-two teeth, disposed in pairs, composed of a sin- 

 gle series of elongated cells, sometimes united and perforated, 

 connected below by a short membrane ; leaf- cells puuctiform 

 above, minutely papillose. 



Genus 83. Leptotrichum. — Peristome of thirty-two teeth, 

 disposed in pairs, or sometimes reduced to sixteen ; leaf-cells 

 narrow, elongated, not papillose. 



Genus 84. Didymodon, — Veil cucullate, covering at least 

 half the sporangium ; peristome rather short, of sixteen linear- 

 lanceolate teeth, consisting of a double row of cells, tender 

 and fugacious, entire, or perforated ; leaf-cells narrow. 



Genus 85. Distichium. — Veil cucullate with a slender beak; 

 peristome of sixteen teeth inserted below the mouth of the 

 sporangium, transversely barred, entire, or perforated ; leaves 

 more or less distichous ; upper leaf-cells minute . 



Genus 86. Desmatodon. — Veil rather large, cucullate ; peri- 

 stome of sixteen subulate teeth, united at the base by a short 

 membrane, often split above, with the divisions free, or united 

 by trabecule ; upper leaf-cells elongated ; lower very large. 



Order XXIX. POTTIEL 



Sporangium straight; peristome wanting, or of sixteen teeth; 

 veil cucullate ; upper leaf- cells large, hexagonal, lower rectan- 

 gular. 



Genus 87. Anacalypta. — Peristome of sixteen teeth, united 

 below by a common membrane, entire, or imperfectly divided, 

 sometimes fragmentary. 



