48 Charles E. Bcsscy 



Family 4. Protopityeae, including Protopitys. (Pf. I, 4, 794.) 

 Family 5. Araucarioxyleae, including Arancarioxylon. (Pf. 



I. 4, 795-) 



Class 28. CORDAITINEAE. Palaeozoic plants, long extinct, 

 related to the modern cycads, and probably also to the conifers, 

 of which indeed they may have been the ancestors. Branching 

 trees, bearing large parallel-veined leaves; seeds with two 

 integuments. 



Family 6. 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. Cordaitcs, 

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



Class 29. BENNETTITINEAE. Mesozoic plants, long ex- 

 tinct, 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 sim- 

 ple, erect, increasing in thickness by annular growth of fibrovas- 

 cular tissue; leaves pinnate; sporophylls in terminal amphispor- 

 angiate strobili. 



Family 7. 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. Benncttites. (Wieland, American 

 Fossil Cycads; Engler's Syllabus, 73.) 



Class 30. CYCADINEAE. Plants with erect, woody, little- 

 branched stems, bearing terminal clusters of pinnate leaves. The 

 collateral fibrovascular bundles are arranged concentrically in the 

 stem ; these increase the thickness of the stem by development of 

 their cambium, and also by the formation of new bundles in the 

 cortical meristem. Sporophylls in dioecious strobili. Many cy- 

 ads which existed in Mesozoic times have become extinct, leaving 

 only a few genera and species in the present. 



Family 8. Cycadaceae. Mostly tropical trees of the present 

 time, with a fern-like or palm-like aspect. Cycas, Dioon, En- 

 cephalartos, Macrocainia, Zamia, Ccrator,amia. (Pf. II, i, 6.) 



Class 31. GINKGOINEAE. Plants with erect, woody, freely- 

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



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