ON GENERA AND SPECIES. 33 



auxilliary characters in the grouping of species, which with 

 his published observations above noticed, I, in time, consi- 

 dered myself competent to publish my views. This I did 

 in a treatise entitled " On Arrangement and Definitions of 

 the Genera of Ferns," which was read before the Linneau 

 Society in 1840, and afterwards published in Hooker's 

 " Journal of Botany," in the volumes for 1841 and 1842, 

 occupying 131 pages, and accompanied by a plate showing 

 the principal forms of venation. In this I characterised 

 143 genera, accompanied by examples of a few of the most 

 typical species of each genus, and with observations on the 

 natural affinities of the genera. Just as my treatise was 

 completed, but before its publication, I received Presl's great 

 work " Tentamen Pteridographese," and it was gratifying 

 to me to find that my views in general coincided with those 

 of that celebrated Pteridologist. I, however, differed from 

 him in some important particulars, chiefly with regard to 

 the relationship of the genera to one another, consequent 

 on the data on which Presl founded his tribes, placing 

 naturally allied species far apart. My endeavour was to 

 associate the species possessing the same general features 

 in respect to their modes of growth (habit), so as to form 

 natural sequences of genera. This I have endeavoured to 

 complete by drawing up a general arrangement, which 

 forms the second part of this volume. 



The following is an abstract of my arrangement in 

 1841 . 



DIVISION I POLYPODIACE^E, R. Br. 



Sporangia furnished with a vertical ring. 



Tribe I. POLYPODIES, J. Sm. 



Sori punctiform, oblong or linear, naked or included 

 under the universal indusium. 

 Sect. I. Orthophlebieae, J. Sm. Veins free. 



