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CONCLUSION. 



It is necessary to say a few words to the subscribers in 

 concluding a work extending over a number of volumes, as, 

 in course of progress, plans become somewhat changed, and 

 alterations take place that were not thought of at the com- 

 mencement of the work. It was intended to publish a large 

 Glossary at the conclusion, but the Addenda to the different 

 volumes has extended the work beyond the prescribed limits, 

 and it was thought desirable that the Glossary should give 

 place to the Addenda. 



In conclusion, I must offer my most hearty thanks to those 

 gentlemen who have so kindly afforded me assistance in the 

 present undertaking, both by supplying me with plants and 

 fronds, and also with works and information on the subject, 

 and in doing so I must more especially mention the great 

 obligations I am under to Sir W. J. Hooker; Mr. Thomas 

 Moore, of the Botanic Gardens, Chelsea; Mr. Joseph Henderson, 

 of Wentworth; Mr. J. Smith, the Curator of the Royal Gardens, 

 Kew; Mr. Moore, of the Glasnevin Gardens; Professor Balfour, 

 of Edinburgh; Mr. Norman, of Hull; Mr. Clarke, of the 

 Glasgow Gardens; Mr. Veitch, Jun., of Chelsea; Mr. Sim, of 

 Foot's Cray; Mr. Rollisson, of Tooting; and Mr. E. Cooling, of 

 Derby. There are many more to whom my thanks ought to 

 be given, and, although not mentioning them personally, to 

 each and all who have rendered me assistance I beg to return 

 my grateful thanks. 



The difficulty in determining imperfectly-known species, (es- 

 pecially where the author has not the advantage of reference 

 to the specimens of the different authorities,) is very great; 

 botanists must therefore welcome as a great boon the valuable 

 works now publishing on the subject, namely, "The Species 

 Filicum" of Sir W. J. Hooker, and the "Index Filicum" of 

 Mr. Thomas Moore. These works, as far as they have already 



