XI. CETERACH. 183 
pinnae, give them a ciliated appearance. The venation is to- 
lerably distinct in young fronds ; but becomes more obscure 
as they get older or when dried. It is arranged thus : at 
the posterior basal corner of each segment, a vein branches 
obliquely from the rachis, and extends in a sinuous course 
towards the apex, and nearer the lower than the upper 
margin ; this produces alternate venules, the first of which, 
directed upwards, alone bears two sori, one on each of the 
two branches into which it separates, the lowest facing the 
rachis, the other turned from it ; the other veins become 
branched near the base, the anterior venule bearing a sorus 
on the anterior side ; consequently all the sori, except the 
lowest, are attached to the anterior side of the anterior 
venules. These branches, however, become again branched 
near the margin, and there anastomose in an irregular 
manner, the points being free, and extending almost to 
the margin. The sori are oblong, at first concealed by 
the scales, and at no time very apparent from the resem- 
blance in colour between them and the scales on the mature 
fronds. The spore-cases are attached to the side of the 
veins, and immediately behind them, seated on the back 
of the vein, is a slightly elevated membranous ridge, which 
probably represents the indusium, and is no doubt the 
" erect white membranous involucre" which is mentioned 
by some writers. 
This plant is found growing on old walls, ruins, churches, 
rocks, and similar situations, and is pretty generally dis- 
tributed over England and Wales, abundant in Ireland, 
rather rare in Scotland, and apparently absent from the 
Northern and Western Isles. It occurs in the middle and 
south of Europe ; in Madeira and the Azores, and in Brazil, 
according to Kunze. 
It is a reputed diuretic, and was formerly used in medi- 
cine, but is now disregarded. 
This is a free growing species under cultivation when 
once established. It dislikes close confinement, and re- 
