Order 19. =Neckeraceæ.= Stems most frequently with flat, leafy
branches. The leaves are smooth, never with longitudinal
folds.--_Neckera._
Order 20. =Hypnaceæ.= The leaves are smooth with square,
often bladder-like, cells at the edge. _Hylocomium_ (_H.
splendens_, _H. triquetrum_); _Hypnum_; _Brachythecium_;
_Plagiothecium_.--_Eurhynchium._--_Homalothecium_, _Isothecium_,
_Orthothiecium_, _Homalia_.--_Climacium_, _Lescuræa_, _Leucodon_.
The Mosses occur all over the globe. Many are found in great
numbers, and growing thickly massed together, they form an
important feature in landscapes (for example _Sphagnum_ and
_Polytrichum_ in the Arctic Tundra). In the Northern and
Arctic regions the Mosses are very plentiful, and often form a
considerable part of the vegetation, while in the Tropics they
are insignificant.
Species of _Hypnum_ and _Polytrichum_, like _Sphagnum_, play an
important part in the formation of peat.