DUBLIlf KATURAL HI8T0ET 80CIBTT. 1 73 



country, especially amid the screen of aged woods, where perpetual shade 

 and moist and even temperature favour its full development. There it 

 may be found extensively mantling the broad surfaces of vertical rocks 

 and of banks, and its drooping and overlapping or imbricated fronds, 

 spreading in masses, display a most lively and delicate green. In such 

 localities II. JFilsoni cannot be traced. It is also more rarely met on the 

 trunks of trees than H. JFihoni, and its habit more sheltered fix)m undue 

 moisture. In the south-western parts of Ireland, in the glens around 

 Killamey, more especially in those of Cromaglouin, and in those of 

 Glouin Caragh, westward of the Reeks, it is met with in all its beauty. 

 In my botanical excursions in the county of Wicklow with the late Mr. 

 Nuttall, I have not met with H. Ikinbrtdgense, although H. Wilsoni is most 

 frequent ; neither have I seen it in Connemara or in Sligo, where, very 

 likely, glens have been explored. In all those localities I have never found 

 a departure from the described habit of growth, nor alteration of the cha- 

 racteristics given, neither any intermingling nor approach of the two spe- 

 cies in the localities which most favour the growth of each. The habits of 

 II. Wilsoni are very different, affecting much more elevated and exposed 

 positions, and greater exposure to atmospheric influence and rain, as well 

 as arid and exposed rocks. In the recesses of the rocks of our highest 

 mountains, particularly their northern and eastern aspects, the M. Wil- 

 soni exhibits- the same characters as found in the more exposed glens, 

 where it coats rocks and trunks of trees with its peculiar crisped, curved, 

 and rather erect habit of growth. On the summits of Brandon, Benis- 

 geach, Cahirconree, and Mounteagle, in Kerry, and even on the cliffs of 

 the Great Blasket Island, this species is met in rich abundance ; but in 

 those localities no approximation can be traced in it to Tunbridgense. 

 Wilsoni is much distributed in the western parts of Ireland, as also in 

 the northern and eastern counties. 



It is clear that in this country H. Tunbridgense delights in localities 

 where shade and a mild and even temperature encourage its growth. In 

 warmer countries and tropical cKmates high altitudes are more conducive 

 to the healthy existence of Hymenophyllum and Trichomanes. Bory de 

 St. Vincent, to whom I shall have particularly to i*efer, mentions in his 

 notes on Algerine Botany the delightful temperature of the province of 

 La Calle, where a perpetual spring exists, for the centigrade thermometer 

 has never stood below 1 1 degrees, nor risen above 30 degrees in the shade. 

 The forests of La Calle abound in beautiful ferns, and where he men- 

 tions the great height of Osmunda regalis, and the gigantic leaves of the 

 ivy. It is singular that he states the male fern, Aspidium filix-maSf does 

 not occur in Africa ; nor, according to " Low's Memoirs" of the plants 

 of Madeira, does the genuine Aspidium filix-mas exist there. HoU, on 

 the Plants of Madeira, alludes only to one species of Hymenophyllum — 

 Tunbridgensey growing at an elevation between 2000 and 3000 feet In 

 the Floras of France the species Tunbridgense is recorded, and is men- 

 tioned as growing on the trunks of trees at Cherbourg. 



I shall now come to a more important point, — the opinion generally 



