78 NATURAL HISTORY SOCIETY OF DUBLIN. 



incline, I think, to the latter opinion, as several of the ITymenophyllece 

 from Reunion have a decided tendency to a unilateral character, and I 

 enclose one specimen of H. Boryanum found by Dr. Meller growing 

 with a mass of that fern and from the same root, which, you will see, is 

 scarcely distinguishable from H. unilaterale. I wish very much I 

 could show you my fernery, which is beginning to be a very good one, 

 and we have also a fine collection of orchids from Madagascar, some of 

 which are quite new and very beautiful." 



In corroboration of such a statement so decided and valuable, I 

 some years since, being much interested with regard to the doubts that 

 existed of the distinctive characters of those two species — Wilsoni and 

 Unilaterale — had the opportunity of communicating direct with Bory 

 St. Vincent at Paris, a short time before his death. His reply — " There 

 absolutely remains to me but one specimen. Wildenow, Yentanal, 

 and the old Jacquine of the neighbourhood (Bourbon), who were then 

 my correspondents of those countries, have not yet found it, no more 

 than three or four other rare species which I have equally exhausted, 

 and which possess but the type of my herbal/' 



Trichomanes longisetum I discovered in the thick forests of the Island 

 of Bourbon. 



Wildenow's description of H. unilaterale is from the communication 

 made to him by Bory St. Yincent: — " Habitat in insulse Borboniae 

 montibus mille orgyas supra mare elevatis, ad rupes humidas." — Bory 

 in Litt. 



The above-quoted letter states that attention has been given by Dr. 

 Meller to the character of air cells ; and in the examination of those of 

 H. unilaterale he finds them to be sufficiently distinct from those of H. 

 Wilsoni, as figured in Seeman's Journal. George Gulliver, F.R.S. t 

 Professor of Anatomy and Physiology in the Royal College of Surgeons, 

 in his Paper on the " Leaf Cells of the British ITymenojphyllice" ob- 

 serves a great distinction between those of H. Tunlridgense and S. Wil- 

 soni, the former being round, or nearly so, and the latter oval, with an 

 average long diameter, and he forms the diagnostics of the two species 

 by terms " sphaerenchyma and ovenchyma." Mr. F. Clowes, of Win- 

 dermere, who has made several communications to me on the subject, 

 states that the fronds of IT. Tunlridgense die annually, while those of 

 H. Wilsoni grow on from year to year. This I can confirm by obser- 

 vations on their growth in my own fernery. In the extract I have 

 given it is further stated that H. Boryanum is scarcely distinguishable 

 from H. unilaterale. The venation of this little fern is similar to that 

 of Tunlridgense, but differs in the hairy underneath part of the frond, 

 and with the branched hairs at the margins. * These involucres are 

 orbicular, ciliated, and sunk in the frond. 



I have had much correspondence with my friend Mr. "Wilson re- 

 garding the interest of the species that he has described, and from my 



* These branched hairs, or forked cilise, are frequent on those ferns of the tropics. 



