276 



PLANT MORPHOLOGY 



4. Filicales 



The Filicales constitute by far the largest order of modern ferns, includ- 

 ing 12 families, about 1 70 genera, and approximately 7,600 species. They 

 make their greatest display in the tropics, but are also well represented in 

 temperate regions. The fossil record of the two most primitive families 

 (Osmundaceae and Schizaeaceae), and possibly of a third one (Gleichen- 

 iaceae), extends back into the Paleozoic, but that of the other families 

 does not reach beyond the Mesozoic. 



Fig. 232. Gleichenia costaricensis, photographed near the summit of the Pods volcano in 

 Costa Rica. 



Families. The Filicales comprise 7 principal families and 5 small ones 

 of minor importance. All of them have living representatives. The 

 chief families are as follows: 



1. Osmundaceae. This is the most primitive family. It comprises 

 3 genera and about 20 species and occurs in both temperate and tropical 

 regions. Osmunda is the principal genus, including over one-half the 

 species. It is widely distributed, three species being found in temperate 

 parts of North America. 



2. Schizaeaceae. This primitive family, including 4 genera and about 

 160 species, is chiefly tropical. Schizaea and Lygodium are widely dis- 

 tributed. Anemia, the largest genus, is found in tropical America, while 

 Mohria is confined to eastern Africa. The family is represented in the 

 Eastern and Southeastern United States by two species of Schizaea, one of 

 Lygodium, and two of Anemia, all of which are rare. 



