308 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



Cretaceous species. Associated with some of the older forms are 

 oval or spherical bodies thought to represent sporocarps. 



The remainder of the living and fossil ferns, excepting certain 

 illy understood extinct types, such as the Devonian and Lower Car- 

 boniferous Arehaeopteridae and the Mesozoic Tempskya, may be 

 grouped together in the Leptosporangiate or Eufilicalean order 

 Polypodiales, although there is some evidence for recognizing the 

 Gleicheniades and Matoniales as independent orders. 



The Polypodiales embrace the great majority of living ferns and 

 include the most specialized and abundant families. Without tak- 

 ing the space to give their diagnostic characters, which appertain 

 more especially to the study of recent forms and are admirably dis- 

 cussed in many texts devoted to that subject, it will be desirable as 

 well as interesting to glance at the geological record of the various 

 families. 



The family Schizaeaceae with between 75 and 100 existing, mostly 

 tropical species, segregated into the genera Schizaea, Lygodium, 

 Mohria, and Anemia, appears to be present as early as the upper 

 Carboniferous in the genus Senftenbergia of Corda, which had small 

 linear pinnules bearing two rows of solitary sessile sporangia, with 

 apical annulae of four or five rows of cells. Triassic forms are not 

 certainly recognized, but the Jurassic genus Klukia with tripinnate 

 fronds shows fructifications that render its reference to this family 

 conclusive. Some of the form-genus Cladophlebis (e. g., C. Brownl- 

 ama from Peru) appear to belong to this family, and during the 

 Lower Cretaceous the genus Ruffordia of Europe and America ap- 

 pears to represent the genus Anemia, while Schizaeopsis, found in 

 a fruiting condition in the Lower Cretaceous of Virginia, repre- 

 sents Schizaea. The genus Acrostichopteris, based upon sterile 

 fronds, which range from the bottom to the top of the Lower Cre- 

 taceous, and found in both Europe and America, also almost cer- 

 tainly represents an extinct type belonging to this family. In the 

 Upper Cretaceous petrified sporangia of the Schizaea type have been 

 found in Japan (Schizaeopteris mesozoica). Undoubted species of 

 Anemia and Lygodium in Europe and America are common and 

 widespread during the Tertiary, the latter genus being often found in 

 fruiting condition. In the poleward spread of subtropical floras 

 in the Eocene and early Oligocene, Lygodium is found as far north 

 as the south of England, Wyoming, and Kentucky, associated with 

 Acrostichum and other tropical forms. 



The family Gleicheniaceae embraces about 100 tropical and sub- 

 tropical gregarious species now segregated to form the genera 

 Gleichenia, Platyzoma, Dicranopteris, and Stromatopteris — the last 

 monotypic on New Caledonia and Platyzoma monotypic in north- 

 ern Australia. 



