FILICINiE. 35 



V. 2365<?. Two long and narrow tubers joined together. Cf. 

 Dunker, "Wealdenbildung, pi. vii. fig. 3 ; also Schenk, Palseonto- 

 graphica, vol. xxiii. pi. xxvi. fig. 1, and Hear, Fl. Tert. Helvet. 

 vol. iii. pi. cxlv. Ecclesbourne. Rufford Coll. 



V. 2700. Very thin stem, 1 mm. broad and 8 cm. long ; matrix 

 penetrated by roots. Ecclesbourne. Rufford Coll. 



v. 2833 and V. 2834. Several tubers of the characteristic shape. 

 Ecclesbourne. Rufford Coll. 



Class riLicmjE. 



Leaves large in proportion to the stem. Sporangia usually occur 

 on the margins or lower surface of ordinary leaves ; occasionally 

 the fertile leaves are distinguished from the sterile by well- 

 marked characters. 



Sub-Class EILICES. 



Isosporous plants. The prothallus (gametophyte generation) 

 usually monoecious, of moderately large size, and capable of an 

 independent existence. The sporangia usually occur in definite 

 groups or sori, with or without indusia. 



INTRODUCTIOJSr TO FILICES. 



Probably no fossil plants are more widely known than the 

 fragments of fern fronds so abundant in the beds of shale asso- 

 ciated with our Coal-Measures. 



"When we come to inquire how far palseobotany has made us 

 intimately acquainted with the general morphology, the minute 

 histology, and the natural affinities of the Coal-Measure ferns, 

 it must be admitted that our scientific knowledge of them is 

 extremely limited. There are certain forms of Palaeozoic ferns, 

 and in the Mesozoic floras there are also a few genera, of which 

 it is possible to speak with confidence as to family, and occasionally 

 as to internal structure ; but such cases are exceptional. The 

 old generic names such as Pecopteris, Sphenopteris, Neuropteris, 

 and others, were instituted as convenient terms by which to 



