32 Charles E. Besscy 



ducing staminate cones, and loose clusters of megasporophylls. 

 Cycas. (Pf. II, I, 6.) 



Family 7. Zamiaceae. Tropical trees of the present time, with 

 both staminate and seed cones. Dioon, Encep'halartos, Macro- 

 samia, Zamia, Ceratoaamia. (Pf. II, i, 6.) 



Class 29. BENNETTITINEAE. "Flowering-plant Ances- 

 tors." Mesozoic plants, long extinct, related on the one hand to 

 the ancient cycads, and on the other to the flowering plants, of 

 which they are thought by some, with very good reasons, to have 

 been the ancestors. Stems simple, erect, increasing in thickness 

 by annular growth of fibrovascular tissue; leaves pinnate; sporo- 

 phylls in terminal amphisporangiate strobili. 



Order Bennettitales. With 'the characters of the class. 



Family 8. Bennettitaceae. Short-stemmed plants with the 

 main axis terminated by a strobilus of sporophylls, the lower 

 sterile and long, the next bearing many microsporangia, and the 

 uppermost megasporangia. Bcnnettitcs. (Wieland, American 

 Fossil Cycads; Engler's Syllabus, 103.) 



Class 30. CORDAITIXEAE. Conifer Ancestors. Palaeozoic 

 plants, mostly long extinct, related to the modern cycads, and 

 probably also to the conifers, of which indeed they may have been 

 the ancestors. 



Order Cordait.\les. Branching trees, bearing large, elongated, 

 parallel-veined leaves ; seeds with two integuments. (Extinct.) 



Family 9. Cordaitaceae. Tall trees (20-30 m. high) bearing 

 subterminal clusters of thick, spirally-arranged, leathery leaves, 

 sometimes as much as i m. long, and 2 dm. wide. Cordaites, 

 Dadoxylon, Artisia. (Pf. II, i. 26.) 



Order Ginkgoales. Maidenhair Trees. Woody, freely- 

 branched trees, bearing fan-shaped, parallel-veined leaves ; the 

 collateral fibrovascular bundles are arranged concentrically in the 

 stem, and these increase its thickness by the development of their 

 cambium ; sporophylls in dioecious strobili. 



Family 10. Ginkgoaceae. Represented today by a single spe- 



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