ON GENERA AND SPECIES. 45 



I have now to notice an important but yet incomplete 

 work, the " Index Pilicum," a synopsis with characters of 

 the g-enera, and an enumeration of the species of Perns 

 with synonyms, and references, &c., &o., by Mr. Thomas 

 Moore, Curator of the Garden of Apothecaries, Chelsea ; 

 the first part of this work appeared in 1857. The author 

 first gives a synopsis of the orders and tribes, followed by 

 a systematic arrangement and characters of the genera, 

 each genus illustrated by a woodcut showing the character 

 of the venation and position of the sori, also an analytical 

 table of the genera and their synonyms. 



With reg-ard to the number of genera the author tells us 

 that he has endeavom'ed " to hold a middle course between 

 the excessive sub-division and the equally inconvenient 

 non-division of older g-enera," and that the classification 

 adopted is based on the plan on which the vascular struc- 

 ture is developed, in conjunction with the nature of the 

 fructification. He enumerates ]86 genera*, which he 

 classifies under five orders, namely, Fulypodiacece, Maratii- 

 acew, Opliioglossacece, Lycopodiacea;., and ilarsileacece. 



The following abstract will be sufficient to convey an 

 idea of Mr. Moore's method of classification. 



FILICALES, SPORE-CASES. 



ONE-CELLED. 



* Spore-cases furnished with a jointed ring, which is 

 usually nearly complete, sometimes rudimentary. 



Ordee L— POLTPODIACE^. 



II Ring vertical, nearly complete. 



Trihe I.— POLYPODINEiE. 



§ 1. Acrosticheas (Ex. ElapJwglossmn, Schott. Acrostichum, 

 Linn.) 



* This includes ten genera of the orders Lycopodiaceae and Marsilia- 

 ce<e, which are not talien up in the present work. 



