定義： a plant that is free-floating on the water surface, not attached to or penetrating the substrate, with some photosynthetic parts in contact with air.
定義： This organism produces this material or substance, either during its life or after death. A produces B if some process that occurs in A has output B.
定義： The important feature of homospory is the four fold division involved in spore production, this takes the form of either a tetrahedra which gives a trilete (Y shaped scar) spore or a tetragon which gives a monolete (single linear scar) spore.
定義： A group of species that exploit the same food resources, and/or use the same feeding or foraging methods. http://en.wikipedia.org/wiki/Guild_(ecology)
