CYCADOPHYTA 355 



Family 7. Zamiaceae. Tropical trees with staminate 

 and seed cones. — Zamia, Macro- 

 zamia, Dioon. 

 Class 29. BENNETTITINEAE. Flowering-plant Ancestors. 

 Mesozoic plants with pinnate leaves, 

 long extinct. 

 Order Bennettitales. With the characters of the cla.ss. 

 Family 8. Bennettitaceae. 

 Class 30. CORDAITINEAE. Conifer Ancestors. Paleozoic 

 to present, trees and shrubs with 

 typically parallel-veined leaves, 

 mostly long extinct. 

 Order Cordaitales. Branching trees with elongated 

 parallel-veined leaves. (Extinct.) 

 Family 9. Cordaitaceae. 

 Order Ginkgoales. Maidenhair Trees. Branching trees 

 with fan-shaped, parallel-veined 

 leaves. (All extinct but one species.) 

 Family 10. Ginkgoaceae. But one genus remaining. 

 — Ginkgo. 

 Order Gxetales. Joint Firs. Anomalous woody plants 

 of doubtful relationship, probably to 

 be placed here, but the sperms not 

 motile. 

 Family 11. Ephedraceae. Small Equisetum-like 

 shrubs with reduced, opposite leaves. 

 — Ephedra. 

 Family 12. Gnetaceae. Shrubs and trees with large, 

 opposite, pinnately veined leaves. — 

 Gnetum. 

 Family 13. Tumboaceae. Short, thick-stemmed 

 woody plants with two large, oppo- 

 site, parallcl-veined leaves. — Turn- 

 boa (Welwitschia). 



Phylum XIII. STROBILOPHYTA. The Conifers 



Minute gametophytes developed in naked seeds produced by 



the large, leafy-stemmed and rooted sporojjhyte^; sperms 



not motile. (Sp. about 400.) 



Class 31. PINOIDEAE. Mostly trees with increasing stents 



