13. Unlike the seed cone of pines, the seed cone of cycads such as Cycas revoluta is ______________. A. a complex structure, a branch of modified branches (microsporophylls) B. a simple structure, a branch of modified leaves (megasporophylls) C. a complex organism, a modified gametophyte D. none of the above are correct

14. In cycads, as in all other gymnosperms, a pollen tube is ______________. A. lacking, the sperm swim freely to the egg B. extremely long, usually more than 15 cm in length C. a means of transferring the pollen grain to the stigma D. one of the most important evolutionary advances in seed plants

15. Cycad fossils are ______________. A. unknown B. known from the late Permian C. abundant in the Devonian, but scarce in later Periods D. never found with cones or seeds

16. The extant gymnosperm phylum known as the Ginkgophyta is monotypic, meaning it has but one ____________. A. seed B. sex C. species D. fossil