Section: Reading

73)

1. A division of the bryophytes, liverworts are relatively small plants which

2. have adapted to different habitats. Two species of liverworts, Riella and

3. Ricciocarpus, thrive in aquatic habitats. Some are found in the company of

4. other vegetation such as mosses, lichens, and sedges in the tundra in

5. Antarctica, while most others prefer moist, shady floors and tree trunks of

6. tropical forests. Leafy liverworts, with two or three rows of lobe-shaped

7. leaves which overlap incompletely, are discovered plentifully in the

8. tropical forests. These plants develop water storage pockets which become

9. home to a host of very small animals. They have a prostrate growth, and

10. single-cell rhizoids -- hairlike projections -- anchor the plant but are

11. incapable of transporting nutrients to the plant. The absence of a midrib is

12. quite common in bryophytes. Sphaerocarpo, a Thallus liverwort,

13. sometimes produces round rosettes or extended, flattened lobes.

14. The bryophytes not only aid soil formation on rocky and unproductive land

15. but balance the moisture content of the soil. Their epidermal cells -- outer

16. cells of the plant -- fused with significant air pores enclose the

17. photosynthetic cells. These pores play a major role in the photosynthetic

18. process in which carbon dioxide is taken in and oxygen is given off.

What is the main topic of the passage?

1. Bryophytes
2. Liverworts
3. Mosses, lichens, and sedges
4. Leafy liverworts

Even though bryophytes, liverworts, mosses, lichens, and sedges are mentioned in the passage, most of the passage deals with different kinds of liverworts. Do not be tricked into choosing (A) even though bryophytes are explained and supported; they are not the main portion of the passage.