MUSCI, mils's' (Lat.., mosses), The technical name of the group of plants known as mosses, one of the two subdivisions of bryophytes, the other being the (liverworts). Mosses are adapted to all conditions, from submerged to very dry, and are most abundantly displayed in temperate and Arctic regions. They have great power of vegetative multiplication, new• leafy shoots putting out from old ones, thus forming thick carpets and cushions. Bog mosses often completely fill up bogs o• small ponds and lakes with a dense growth which dies below and con tinues to grow above. These quaking bogs or 'mosses' furnish very treacherous footing. In their depths the dead moss plants become slowly modified into peat.
There are two great groups of mosses, the Sphagnum forms (peat. or bog mosses) and Bryum forms (true mosses). The life history of a true moss shows a distinct alternation of generations (q.v.). When a spore germinates, there is first developed a small, green, thready body (protonema), upon which appear buds that give rise to the ordinary leafy moss plant. Upon
this leafy plant the sex organs (antheridia and archegonia ) are borne ( Fig. 1 and hence it is the sexual phase (gametophyte) in the alternating generations. The sex organs produce a fertilized egg. which upon germination does not reproduce a leafy moss plant, hut a structure of totally dif ferent character, namely a stalked spore-case (sporogonium), full of asexual spores, commonly called the moss 'fruit.' Since this sporogonium has no sex organs, it is the sexless phase (sporo phyte) in the alternation. When these spores germinate they produce leafy moss plants (game tophytes) again, and so alternation continues. (See Fig. 2.) The spore-case (capsule) of an or dinary moss, generally pendent from a slender stalk (seta), is a very complicated structure. It is usually somewhat urn-shaped. with a little coni cal o• flattish lid (operculum), which is off when the spores are to be discharged. Often quite common in the Tertiary rocks and especial ly so in the amber.