16 ALLOSORUS 
they are alternate on the branchlets, and the leafits 
and their lobes are also alternate. 
By " alternate " is meant, first on one side, and then 
one on the other side, each leaflet, leafit, and lobe, being 
opposite to the space between two leaflets, leafits, or 
lobes, on the contrary side. The leafits of the barren 
fronds are pale bright green, wedge - shaped, finely- 
toothed on the edges, and frequently crisped or curled. 
The fertile fronds are considerably taller than the barren 
fronds, and their leafits are spear-head-shaped, and 
smooth-edged. The fructification, or sori, are in lines 
along the under margin of the leafits, as represented in 
the magnified leafit of our engraving, but the margin is 
so rolled back as to conceal the sori, as on one side of 
the leafit in that engraving. After the spores or seeds 
have ripened and been discharged which in their 
native state occurs in September the sori so spread 
out, that they cover the whole of the back of the leafit, 
except its midrib. 
In our engraving, which is of the natural size, the 
fertile frond is in the centre 
Allosoms crispus is a 1'eru rather rare in this country, 
being confined to its northern parts and mountains. It 
affects rocks, heathy places, and old walls. It has been 
found in Rutlandshire ; at Tenterfell, near Kendal, in 
Westmoreland ; on Cader Idris, in Merionethshire ; 
and on Snowdon, in Carnarvonshire; at Borrowdale,.in 
Cumberland ; and in the Highlands of Scotland. 
It was unknown to old Gerarde and to bis editor 
Johnson ; nor do we find any mention of it as a native 
