FEKNS: CLASSIFICATION. 295 



Classification of the Pteridophytes. 



Of the living pteridophytes four classes may be recognized. 

 CLASS FILICINEJE.* 



This class includes the ferns. Four orders may be recognized. 



600. Order Ophioglossales. (One Family, Ophioglossacese). This order 

 includes the grapeferns (Botrychium), so called because of the large 

 botryoid cluster of sporangia, resembling roughly a cluster of grapes; and 

 the adder-tongue (Ophioglossum), the sporangia being embedded in a long 

 tongue-like outgrowth from the green leaf. Botrychium and Ophioglos- 

 sum are widely distributed. The roots are fleshy, nearly destitute of root 

 hairs, and contain an endophytic fungus, so that the roots are mycorhiza. 

 The gametophyte is subterranean, and devoid of chlorophyll. In Botry- 

 chium virginianum, an endophytic fungus has been found in the prothal- 

 lium. Another genus (Helminthostachys) with one species is limited to 

 the East Indies. 



601. Order Marattiales (One Family, Marattiaceae). These are trop- 

 ical ferns, with only four or five living genera (Marattia, Danaea, etc.). 

 They resemble the typical ferns, but the sporangia are usually united, sev- 

 eral forming a compound sporangium, or synangium. ^ 



The Ophioglossales and Marattiales are known as eusporangiate ferns, 

 while the following order includes the leptosporangiate ferns. 



602. Order Filicales. This order includes the typical ferns. Eight 

 families are recognized. 



Family Osmundacece. Three genera are known in this family. Os- 

 munda has a number of species, three of which are found in the Eastern 

 United States; the cinnamon-fern (O. cinnamomea), the royal fern (O. 

 regalis), and Clayton's fern (O. claytoniana). No species of this family 

 are found on the Pacific coast. 



Family Gleicheniacea. These ferns are found chiefly in the tropics, and 

 in the mountain regions of the temperate zones of South America. There 

 are two genera, Gleichenia containing all but one of the known species. 



Family Matoniacece. One genus, Matonia, in the Malayan region. 



Family Schizceacea. These are chiefly tropical, but two species are 

 found in eastern North America, Schizaea pusilla and Lygodium palma- 

 tum, the latter a climbing fern. 



Family Hymenophyllacea. These are known as the filmy ferns because 

 of their thin, delicate leaves. They grow only in damp or wet regions, 

 mostly in the tropics, but a few species occur in the southern United States. 



Family Cyatheacece. These are known as the tree-ferns, because of the 



* As class Filicales in Engler and Prantl. 



