Nov , 1913.] The Classification of Plants, X. igg 



steles of known Pteridophytes is too great to be bridged unless 

 fossil fomis can be found intennediatp between the two. Since 

 these forms should be discovered in the Ordovician, Silurian, or 

 Cambrian rocks or perhaps in deposits of even earlier age, there is 

 no immediate prospect of their coming to light even if any were 

 preserved. The Silurian and Ordovician should be thoroughly 

 searched for Pre-Devonian Pteridophytes for Ordovician fossils 

 might give a clue as to the possible path along which the vascular 

 plants evolved. In the meantime it is most reasonable to classify 

 our living species on the basis of their entire morphology both 

 internal and external. 



Correction. 



Through inadvertance the genus, Microcycas appeared as Micro- 

 zamia in the IX paper of this series (Ohio Naturalist 13: 106). 

 Read Microcycas instead of Microzamia. 



In the following synopsis the segregation has been carried as 

 far as the genus except in the complex Polypodiaceae which well 

 deserve an independent treatment. 



Synopsis of the Ptenophyta. 



I. Sporophyte homosporous, having only one kind of nonsexual spores; 

 leaves usually large and mostly compound; gametophytes comparatively 

 large, hermaphrodite or unisexual. Filices. Ferns. 



1. Plants eusporangiate, sporangia developed from internal cells. 



EUSPORANGIAT^-E. 



(1). Sporangia on a special sporangiophore distinct from the 

 leaf-blade; gametophvte subterranean, without chlorophvll. 

 OPHIOGLOSSALES'. ophiogloss.\ce^. 



a. With reticulate venation; sporangia in a single row on 

 both margins of the sporangiophore. Ophiogossum. 



b. With dichotomous venation, sporangia clustered on the 

 sporangiophore or the sporangiophore more or less 

 branched. 



(a). Sporangia opening transversely; on the margin of 



a more or less branched sporangiophore. Botrychium 



(b). Sporangia opening longitudinally; in little clusters. 



Helminthostachys. 



(2). Sporangia on the underside of foliage leaves; leaves with 



two stipules; gametophytes with chlorophyll. 



MARATTIALES. 



a. Sporangia in sori but free from each other. 



ANGIOPTERIDACE.^. 



(a). Sori very long, with 80-160 sporangia; leaves simply 

 pinnate. Archangiopteris. 



(b). Sori short, elliptical, mostly with 10 sporangia, 

 sometimes less or sometimes as high as 20; leaves 

 two or more times pinnate. Angiopteris. 



b. Sporangia united forming synangia. 



(a). Each loculus or sporangium of the synangium 

 longitudinally dehiscent, marattiace.e. 

 ((a)). Synangia elongated, oval, venation not 

 reticulate; leaves large pinnately com- 

 pound. Marattia. 



