210 Linnean Society. [Feb. 1, 



February 1. 



R. Brown, Esq., President, in the Chair. 



Daniel Oliver, jun., Esq., and William Thomson, Esq., were 

 elected Fellows. 



Read a paper " On Venation as a generic character in Ferns ; 

 with Observations on the genera Hewardia, J. Smith, and Cionidium, 

 Moore." By Thomas Moore, Esq., F.L.S., Curator of the Botanic 

 Garden, Chelsea. 



The object proposed by the author is to inquire — 1st, into the 

 general importance of modifications of the vascular structure of the 

 fronds in distinguishing the genera of Ferns ; and 2ndly, into their 

 relative value in the cases instanced. He-begins by referring to the 

 numerous authors by whom the venation has been turned to account 

 in the formation of genera or subgenera, and in particular to the ob- 

 servation of Mr. Brown, that " for subdivision, the most obvious as 

 well as the most advantageous source of character seems to be the 

 modifications of the vascular structure, or the various ramifications 

 of the bundles of vessels or veins of the frond, combined with the 

 relation of the sori to their trunks or branches." He notices an in- 

 stance in which Sir William Hooker has given generic importance 

 to this character of venation alone, viz. in Dictyoxiphium ; while in 

 Schizoloma he regards the venation as only of subgeneric value ; and 

 he treats it as a mere question of words, to be decided by conve- 

 nience, whether or not this character should be generically em- 

 ployed. In the case for instance in reference to which Mr. Brown's 

 remarks were made, Polypodium (Dipteris) Horsfieldii, it seems to 

 him, as a matter of convenience, a much simpler and more easily 

 comprehensible idea, to regard Dipieris as a group of ferns with 

 round naked sori, dichotomous primary veins and reticulated ve- 

 nules, than to have to recognize in Polypodium (a genus of ferns 

 having round naked sori) an included group called Dipteris, in 

 which the primary veins are dichotomous and the secondary reti- 

 culated. In most cases, indeed, he regards subgenera as at the best 

 but cumbrous contrivances. 



Looking at the question of venation, as illustrated in the great 

 and universally adopted natural divisions of flowering plants, he 

 thinks its generic importance in ferns rests on better grounds than 

 convenience alone. In the case of flowering plants the presence of 

 complete floral organs affords the necessary diversity for generic 



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