FIGURE 22–11 Moss Life Cycle This life cycle shows the dominance of the gametophyte stage that is typical of mosses and other bryophytes. Interpret Visuals In which structure are eggs found?

d

▸ Gametophyte When a moss spore lands in a moist place, it sprouts and grows into a tangled mass of green filaments. Figure 22–11 shows the life cycle of a typical moss. As this young gametophyte grows, it forms rhizoids that grow into the ground and shoots that grow into the air. These shoots grow into the familiar green moss plants.

Gametes are formed in reproductive structures at the tips of the gametophytes. Some bryophyte species produce both sperm and eggs on the same plant, whereas other species produce sperm and eggs on separate plants. Eggs are produced in archegonia (ahr kuh GOH nee uh; singular: archegonium). Sperm are produced in antheridia (an thur ID ee uh; singular: antheridium). Sperm and egg cells fuse to produce a diploid zygote.

▸ Sporophyte The zygote marks the beginning of the sporophyte stage of the life cycle. It develops into a multicellular embryo, growing within the body of the gametophyte and depending on it for water and nutrients. Eventually, the sporophyte grows out of the gametophyte, and develops a long stalk ending in a capsule that looks a bit like a salt shaker. The spore capsule is called a sporangium (spoh RAN jee um; plural: sporangia). Inside the capsule, haploid spores are produced by meiosis. When the capsule ripens, it opens, and haploid spores are scattered to the wind to start the cycle again.

In Your Notebook Classify each of these moss structures as gametophyte or sporophyte: sporangium, spore, archegonium, zygote.

Table of Contents