i64 GYMXOSPERMS 



KEY TO THE GENERA OF CYCADACEAE — Continued 



(c) Sporophylls with a long median spine 



— Australia 8. Macrozamia 



(d) Male sporophylls with a flat top; fe- 

 male sporophylls with a shield shaped 



top — Cuba 9. Microcycas 



The "sporophylls in longitudinal rows," as given for Zamia is, of 

 course, entirely wrong. The arrangement is strictly spiral, but so 

 regular that the sporophylls appear to be in rows. This appearance 

 is not at all confined to Zamia. 



When the plants have cones, the genera can be identified positive- 

 ly. Stangeria and Microcycas are monotypic. Bowenia has only two 

 species, both easily recognized. Dioon has three, and perhaps four, 

 species, all easily recognizable. Ceralozamia has two, and, possibly, 

 three good species and a lot of variants which taxonomists classify 

 as species, subspecies, varieties, or forms, categories of no interest to 

 the morphologist, except that they show how a plant may vary. The 

 other genera, Cycas, Encephalartos , and Zamia, have numerous spe- 

 cies, some of which have not been described adequately and never 

 will be accurately described until there has been a prolonged and de- 

 tailed field study. Until such a study has been made, the descrip- 

 tions of species, subspecies, varieties, and forms in the more difficult 

 regions of a genus will continue to degenerate into descriptions of 

 individuals, which burden the literature, while the plants may or 

 may not ever occur again. 



Although the family has persisted from the Upper Paleozoic up to 

 the present time, there is not sufficient material to make a key to the 

 extinct members. 



