CHAPTER VIII 

 CYCADALES — Continued 



PHYLOGENY 



A study of the life-history of any group should make the investi- 

 gator try to determine what its ancestry may have been and try to 

 find whether it has left any progeny. 



The "living fossil" character of the Cycadales makes them par- 

 ticularly favorable for a study of phylogeny, because the ancestors, 

 which must have flourished in the Upper Carboniferous, are the best 

 known of any fossil plants. 



Without going into any detailed discussion, it may be assumed 

 that the Cycadales have come from the Filicales either directly or 

 through the CycadofiHcales. It is true that the lycopod line was 

 very well represented in the Carboniferous, but paleobotanists agree 

 that this line has not given rise to either the Cycadales or the Ben- 

 nettitales. 



The fern leaves of that period are nearly always pinnate, more 

 often twice or thrice pinnate than once pinnate ; and the CycadofiH- 

 cales are similar, with more than once-pinnate leaves prevaihng. As 

 far as the leaf is concerned, the cycads might have come from either 

 group. 



But, as shown in an earher chapter, we think it has been proved, 

 as far as anything can be proved in phylogeny, that the CycadofiH- 

 cales came from the Filicales. Lines of evolution do not progress at 

 the same rate: one organ may progress rapidly while another re- 

 mains stationary. The cycads retain the swimming sperm, but have 

 lost the wall between the ventral canal nucleus and the egg nucleus; 

 while in the pines the sperms have lost the swimming character but 

 still keep the wall between the ventral canal nucleus and the egg 

 nucleus. In Stangeria, the leaf is so fernlike that the genus was placed 

 in the Polypodiaceae, of the true ferns — even in the genus Lomaria; 

 but it has lost the wall between the ventral canal nucleus and the 



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