62 HISTOllY OF BRITISH PERNS. 



the venules lying parallel, and extending in straight lines 

 towards the margins, terminating in the barren fronds 'in 

 the serratures of the margin, but in the fertile fronds 

 extending into the indusium, there forming the receptacles 

 to which the spore-cases are attached. The sori are oblong, 

 covered by indusia of the same form, each consisting of the 

 apex of one of the lobes of the frond, changed to a mem- 

 branous texture, and folded under. The sori are, as already 

 mentioned, seated on this membranous reflexed lobe, and 

 by this circumstance the genus may at once be detected by 

 those who are not conversant with its easily recognized 

 prima facie appearances. 



The Maiden-hair is a local plant, though it has a wide 

 geographical range. It is found here and there in the 

 warmer parts of Great Britain and Ireland, evidently pre- 

 ferring cavernous and rocky situations within the influence 

 of the sea. What is believed to be the same species is 

 found in the warmer parts of Europe, in Asia, in the north 

 of Africa, and in the Canaries arid Cape de Yerd Islands. 



It is, moreover, a tender plant, and does not thrive under 

 cultivation in the climate even of the south of England, 

 unless sheltered in a frame or green-house, or by being 

 covered with a glass. In a Wardian case it grows well ; 



