1 74 DUBLIN NATTJRAl HISTOET SOCIETY. 



entertained by botanists, that Hymenophjllum Wilsoni of British botany 

 is none other than the H. unilaterale of Willdenow's *' Species Planta- 

 rum," p. 521. We are aware how very nearly some of the exotic Tricho- 

 manes and Hymenophyllums approach in form and habit of growth ; yet 

 the character and position of the involucra in many species are very dif- 

 ferent What may be the true characteristics of the involucra of JE. uni- 

 laterale, we are in some measure left to conjecture. Ko descriptive terms 

 can clearly determine the doubts entertained of a species. Accurate 

 drawings of the recent plant, or authenticated specimens, should only be 

 advanced as confirmatory of the decision of disputed views. Again, there 

 are difficulties of deciding species of exotic ferns, when reference is to an 

 ill-preserved Herbarium, and where accurate notes do not exist of pecu- 

 liarity of locality and of habit. According to Hooker's '' Species Filicum," 

 If. imilaterale of Willdenow, from a specimen from Martins, proved to be 

 the species Tunbridgense, and H. unilaterale of Willdenow, according to 

 description, was JT. Wilsoni, but not according to a specimen from Martins. 

 Some years since, being much interested in the affinities ofTrichomanes 

 of this country with the forms of Trichomanes alatum and T. radicans of 

 Jamaica, I had many communications with that amiable and liberal pro- 

 moter of science, Sir William Jackson Hooker, Director of the lloyal 

 Gardens, Kew. I had also favourable opportunities of communicating 

 with the celebrated Bory de St. Yincent, from the desire of knowing the 

 characters, and obtaining specimens of Trichomanes longisetum and of 

 Ilymenophyllum unilaterale, discovered by him in the Isle of Bourbon. 

 I give an extract from his reply, dated Paris, 14th of February, 1845 : — 

 "The plants which interest you were discovered by me in the thick 

 forests of the Island of Bourbon, and these were communicated at the 

 time to Willdenow, to Ventenal, and to the old Jacquine of the neigh- 

 bourhood, who were then my correspondents of those countries. They 

 have not yet found them, no more than three or four other rare species." 

 There, therefore, does not really exist in any of the herbaria in Britain 

 an authentic specimen of the Hymenophyllum unilaterale of Willdenow. 

 Under these circumstances, and with reference to the habits of the two 

 species of this country, I would venture to suggest that the species 

 Wilsoni be retained in the list of our Irish ferns as a slight tribute to 

 the merit of so zealous an observer, and so distinguished a cryptogamic 

 botanist, as William Wilson, Esq., of Warrington, who, in August, 1829, 

 first drew attention to the distinction, in the neighbourhood of Killamey, 

 of the two species of Hymenophyllum.] 



William Andeews, M. R. I. A., President, read the following 

 paper : — 



FUETHETl EEMAEKS ON HYMENOPHYLLUM. 



I wouxD not again have trespassed on the Meeting, but I was desi- 

 rous of giving some explanation with regard to the habitats of the 

 species of Hymenophyllum, which my last statement, perhaps, did not 



