11. The extinct \"cycadeoids\" differ from the modern extantcycads by having ______________.

A. primary tissues but no secondary tissues

B. unisexual pollen and seed cones

C. different morphology of the guard cells in the epidermis

D. flowers instead of cones

12. Cycads are dioecious, meaning that ______________.

A. there are no reproductive structures known

B. the plants drop their leaves each fall

C. there are separate male and female plants

D. they have male and female cones on the same plant

13. Unlike the seed cone of pines, the seed cone of cycads suchas 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 seedplants

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