Chapter Summary

1. Flowering plants (angiosperms) have ovules and seeds completely enclosed within carpels; the carpels comprise ovaries that become fruits. There is one phylum of flowering plants (Magnoliophyta); it is divided into two classes (dicots and monocots).

2. Englerian botanists believed flowering plants evolved from conifers. Most contemporary botanists hypothesize they evolved separately from pteridosperms and that the first flowers had many separate, flattened parts spirally arranged on an elongate receptacle.

3. Flowering plants are heterosporous.

4. Flowering plant gametophytes develop in separate structures. The female gametophyte (megagametophyte) develops in the ovule. Integuments, which later become a seed coat, surround the megagametophyte. Pollen grains developed in anthers become male gametophytes.

5. Pollination is the transfer of pollen grains from an anther to a stigma; it is brought about by insects, wind, and other agents.

6. After pollination, a pollen tube may grow from a pollen grain to the female gametophyte; the tube nucleus remains at its tip, and the generative nucleus divides, producing two sperm nuclei.

7. Following the discharge of the contents of the pollen tube into the female gametophyte, a sperm nucleus unites with the egg, forming a zygote; the other sperm nucleus simultaneously unites with the two central cell nuclei, forming a 3n endosperm nucleus.

8. The endosperm nucleus becomes nutritive endosperm tissue that may become part of the seed or be absorbed by the seed's embryo.

9. Due to variations in how a female gametophyte develops, some flowering plants produce 5n, 9n, or 15n endosperm tissue.

10. Some artificial grouping of flowers to aid identification does not reflect natural relationships. Sources of evidence used to try to group plants naturally include fossils, which suggest the flowering plants first appeared about 160 million years ago.

11. Primitive flowering plants had simple leaves and numerous spirally arranged flower parts that were not fused to each other; they possessed both stamens and pistils and were radially symmetrical (regular).

12. Specializations include a reduction in the number of parts, fusion of parts, appearance of compound pistils composed of several individual carpels, inferior ovaries, bilateral symmetry (irregular flowers), and unisexual flowers.

13. Monoecious species have both male and female flowers on the same plants; dioecious species have male and female flowers on separate plants.

14. Bee-pollinated flowers are delicately sweet and fragrant and tend to be blue or yellow in color.

15. Beetle-pollinated flowers tend to have stronger odors and are usually white or dull in color.

16. Some fly-pollinated flowers emit foul odors.

17. Moth-pollinated flowers tend to be white or yellow.

18. Bird-pollinated flowers are usually bright red or yellow and have much nectar but little odor.

19. Most orchids produce pollen grains in pollinia that adhere or clamp onto parts of visiting insects. The flowers of some orchid species have developed bizarre pollination mechanisms.

20. Herbaria are essentially libraries of dried, pressed or otherwise preserved plants, fungi, and algae arranged so that specific specimens may be readily located. Properly preserved plants may last for hundreds of years.

21. A plant to be pressed is placed in a plant press between sheets of newspaper and absorbent material. Dry specimens are affixed to sheets of high-quality paper, with a label giving collection information.

22. Plant parts may be pressed for artwork, place mats, and so on. Flowers may be preserved three-dimensionally.

23. Because so many plants are now on rare and endangered species lists, collectors should try to confine their future collecting to photographs as much as possible.