CYCADALES 6i 



practically throughout the Mesozoic, and there were cycad-like 

 leaves in the Permo-Carboniferous. Megasporophylls of Cycadospa- 

 dix hennoquei, from the lower Liassic, differ less from those of the 

 living Cycas revoluta than those of Cycas revoluta differ from some of 

 the other living species of the genus. Records are more abundant in 

 the Jurassic; and the group reached its widest distribution and 

 greatest display in the early Cretaceous. Then it began to decline, 

 so that the living cycads are less abundant than their prede- 

 cessors. 



The lack of a satisfactory geological record is partly compensated 

 for by the fact that the cycads have come down from the remote past 

 with so httle change that, if one could be transported back a hundred 

 million years, he would doubtless recognize some of the genera. The 

 cycads of today may well be called "living fossils." 



There is only one family, the Cycadaceae, with only nine genera, 

 four of which belong to the Western Hemisphere, and five to the 

 Eastern. In a recent monograph, Schuster^'" recognizes 65 species; 

 but with his subspecies, varieties, and forms — categories of no in- 

 terest to the morphologist — ^the number is much larger. We prefer 

 to regard a species as a norm which may vary considerably in many 

 directions. Giving names to variants, which may never occur again, 

 merely makes confusion and burdens the nomenclature. If all genera 

 and species had been described by competent observers who had 

 studied them in the field, taxonomy would not have so many species 

 to deal with. 



GEOGRAPHIC DISTRIBUTION 



In the Mesozoic, the cycads were world-wide in their distribution, 

 as cosmopolitan as Pteris and Typha are today; but now they are 

 confined to tropical and subtropical regions, and even there they 

 occur in scanty patches, in out-of-the-way places, so that coUecting 

 involves hard tramping, of ten over rocky, inhospitable ground, where 

 natives as well as nature seem to conspire against success. 



The great cycad regions of the world are Mexico and the West 

 Indies, in the Western Hemisphere ; and Australia and South Africa 

 in the Southern Hemisphere. Only two genera occur outside of these 

 regions: Zamia, in the West, and Cycas in the East. 



