Club Mosses
Club moss also called ground pine, are mainly native to tropical mountains. Club mosses are evergreen herbs with needlelike or scalelike leaves and, often, conelike clusters of small leaves (strobili), each with a kidney-shaped spore capsule at its base. An underground sexual phase plant (one that produces gametes, or sex cells), alternates in the life cycle with the spore-producing plant.
Most club mosses creep or trail although some have erect stems. The leaves are small and in addition to the ordinary green leaves, club mosses have fertile leaves (sporophylls). The leaves, which project above the soil level, are the only photosynthetic part of the plant; the rest survives as a corm (a condensed stem) underground. Each sporophyll has a single large spore receptacle, or sporangium, on its upper surface near the base of the leaf. The sporangium may be globular or kidney-shaped.
In club mosses the spores are released when they ripe – the sporangium splits open and the spores are dispersed by the wind. In quillworts the spores have to wait until the sporangia decay before they can be released.
The life cycle of club mosses consists of two alternating phases – the gametophyte generation and the sporophyte generation. The gametophyte phase begins with spores which germinate into prothalli and ends with the fertilization of the female gametes by the male sperm. The sporophyte generation begins with the fertilized egg (zygote) which develops into the spore-producing plant.
Reproduction among the club mosses is, however, not always sexual – in some species leafy stem structures called bulbils detach themselves from the plant and develop into new plants.