21 BRITISH EOCENE FLORA. 



" This last type comes near that of Tceniopteris (fig. 7), in which, however, the midrib 

 is very much elongated, the secondary veins exceedingly numerous, given off at right, or 

 not very acute angles, and never divergent, but either convergent (towards the midrib) 

 or rectilineal. 



" In the Alethopterisiy^G (fig. 5) the midrib is slender, and gives off short rectilineal or 

 slightly convergently curved secondary veins at acute angles ; ternary veins are wanting, 

 or only proceed from the lowest secondary ones, and only on one side (of the pinnule). 



Fig. 5. — Alethopteris. Fig. G. — Pecopteris. 



" In the Pecopteris type (fig. 0) the undivided or forked secondary veins spring from 

 the midrib, which is distinctly continued to the apex, at slightly acute angles, and send 

 out ternary veins [ex. Gleichenia Hantoneusis and Osnmnda lignitim). 



" Whereas in the foregoing types of venation all the veins are free^ in the following 

 some or all of them anastomose with each other. Those of the Goniopteris type (fig. 8) all 

 anastomose, or at least the inner ternary veins, and remain undivided. The two 

 anastomosing veins blend in one called the ray, which runs through in the Goniopteris- 



FiG. 7. — Taeniopteris. Fig. 8.— Goniopteris. 



Aspid'ii type, that is to say, it extends to the point of union of the next pair, whilst in 

 the Goniopteris Alcniscii type {Phegopteris prce-cusjndata ; PI. IV, fig. 9) they terminate 

 before reaching the union. All the ternary veins are united in the latter type, but in 

 that of G. Aspidii [Phegojjteris Bunhurii, PI. V) some of them are free. 



" When the ternary veins form a network in which there is a row of larger meshes 

 on either side of the midrib or secondary veins, we have the Dictyopteris type. In this 

 either all the veins are connected in a network (Z). simplex), or the secondary ones are 



