If you were asked to name the parts of a plant, you probably would list roots, stems, leaves, and perhaps flowers. You may also know that many plants grow from seeds. But did you know that some simple plants have none of these parts? Nonvascular plants, the bryophytes, don't have roots, stems, or leaves. They do have rootlike fiber, stalks that look like stems, and leaflike green growths. Instead of growing from seeds, bryophytes grow from spores. The nonvascular plants include mosses and liverworts.
Mosses.
A moss is a simple rootless plant with leaflike growths in a spiral around a stalk. Moss plants are held in place by rootlike filaments or threads made up only a few long cells called rhizoids. One type of liverwort is a simple, rootless plant that has a flattened, leaflike body. Liverworts get their name because, to some people, they look like a liver. The ending, -wort, meansherb,? so the word liverwort meansherb for the liver.? In liverworts rhizoid is made up of just one cell. Both mosses and liverworts grow in damp areas and range in size from 2 to 5 centimeters in height.
Of approximately 20 000 species of nonvascular plants, most are classified as mosses. Have you ever seen mosses growing on tree trunks, rocks, or the ground in damp or humid areas?.
The Moss Life Cycle.
A typical growth of moss plants looks like a soft, green carpet on the forest floor. Sporophyte is the spore-producing diploid stage in the moss life cycle. It includes a stalk and a capsule in which numerous haploid spores are produced. Eventually, the capsule breaks open and the spores are scattered. When a haploid spore lands on wet soil or rocks, it germinates into a thin, threadlike green structure. Within a few days, small gametophyte moss plants begin to grow here and there along the thread. A gametophyte is the form of a moss plant that produces sex cells. Sometimes, a moss gametophyte produces only male or female sex cells, but often both types are produced.
