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XX. Characters of Hookeria, a new Genus of Mosses, with De- 

 scriptions of Ten Species. By James Edward Smith, M. D. 

 F.R.S. P.L.S. 



Read April 5, 1808. 



Since the publication of a paper on the Generic Characters of 

 Mosses, and particularly of the Genus Mnium, in the 7th volume 

 of our Transactions, an excellent treatise on the same subject, 

 more especially respecting Orthotrichum and Neckera, by Dr. 

 Mohr of Kiel, has appeared in the last fasciculus of the Annals 

 of Botany, of Dr. Sims and Mr. Konig; a publication whose 

 discontinuance I always find fresh reason to lament, whatever 

 botanical subject I touch upon. The able cryptogamist, to 

 whom we are obliged for this treatise, tries all the genera of 

 which he has occasion to speak, by the Linnaean rule "genus 

 dabit character em" and the result is no less in favour of his 

 acuteness than of the excellence of the rule. In order to cha- 

 racterize genera which nature shows by their habit to be di- 

 stinct, he has paid more attention to the form and structure of 

 the calyptra than any preceding writer, and I think with good 

 success. He expresses some " doubts of the propriety of having 

 " recourse to the form and structure of the capsules of mosses 

 " in forming their generic characters/' lest it should " oblige us 

 44 to divide Polytrichum and other genera into several new ones* 

 " and to make more such unnatural alterations." In answer to 

 this, 1 beg leave to remind him of the rest of the Linnaean rule, 



that 



