ON GENERA AND SPECIES. 27 



work consists of quarto plates, each plate illustrating a 

 genus by figures, showing a portion of the fronds natural 

 size and also magnified, in which the anatomical structure 

 (venation) and the form and position of the sori and other 

 parts of the fructification are distinctly shown, each plate 

 being accompanied with descriptive letterpress. At the 

 time of the author's death, only forty plates of this prac- 

 tical and useful work were published. 



With the works of Schott and Brown commenced a new 

 era in the history of Pteridology. It is, however, to Pro- 

 fessor Presl, of Prague, that the credit is due of being the 

 first to publish a general systematic arrangement of 

 genera founded on venation, which appeared in 1836 in 

 his celebrated work entitled " Tentamen Pteridographese." 

 In that work about 1,500 species of annulate Ferns are 

 enumerated (exclusive of the tribes Hyinenophyllece and 

 Osmundece), which he classifies under 115 genera arranged 

 under two sub-orders, technically distinguished by the dif- 

 ference in the direction of the ring that surrounds the 

 sporangium. The first he terms Helicogyratce, which is 

 characterised by the ring being horizontal or more or less 

 oblique with its point of attachment, it contains two tribes, 

 viz. : Gleicheniacece, and Cyatheacece^ the first of which has 

 five genera and twenty-three species ; the second eight 

 genera and twenty-four species. The second sub-order is 

 termed Cathetogyratoe, and contains all Ferns in which the 

 ring of the sporangia is vertical. 



The following is an abridgment of Presl's arrange- 

 ment : 



ORDER I. FILICES. Presl 



Sub-Order I. HELICOGYRAT^S, Bernh. Ring horizontal or 

 oblique. 



