486 



PAIwEOBOTANY. 



smaller ferns, the genera Sphenopteris, Pecopteris, Alethopteris, 

 Odontopteris, Neuropteris, Hymenophyllites, and Cyclopteris may 

 be mentioned as the most important and widely distributed. 

 In the genus Neuropteris (fig. 384) the midrib of the leaflets is 



Fig. 384. Neuropteris heterophylla. Coal-measures of Europe. The lower figure 

 shows a single leaflet enlarged. 



evanescent, either not distinct, or disappearing towards the 

 apex. Species of this genus are found in the Coal-formation 

 over almost the whole world. In Alethopteris the leaflets are 

 attached by their bases to the stem and to one another, and 

 are provided with a very distinct midrib from which the veins 

 are given off nearly at right angles. The commonest species 

 is the cosmopolitan Alethopteris (Pecopteris') lonchitica, which 

 nearly resembles the living Brackens (Pteris aquilina). Nearly 

 allied to Alethopteris is the genus Pecopteris, which includes a 



