S3 PEKNS 0¥ GEEAT BRITAIN. 



base being the broadest, 'the upper ones becoming 

 gradually narrower, but all of the same general shape. 

 They are deeply pinnatifid, each segment attached by 

 the whole of its base, and connected by a widening of 

 its base to the segment behind it. When the frond 

 attains a greater luxuriance,' the pinnae become longer, 

 and their pinnules more remote, and the margins of the 

 lobes of the pinnae have rounded notches. 



The mid-vein of the lobes is winding, the lateral 

 branches being again divided into several branches, that 

 nearest the upper end of the lobe bearing the circular 

 clusters of fructification, which are thus seated about 

 half-way between the mid- vein and the margin, and 

 generally found only on the upper part of the frond. A 

 flat kidney-shaped indusium covers the clusters, and its 

 margins, though uneven, are not torn. The fructification 

 is matured in August and September, soon after which 

 the fronds perish by the frost. 



A fern which is so nearly allied in some points to this 

 species, and in others to the characters of Lastrea spinu- 

 losa, that it might be regarded as a variety of either, is 

 sometimes termed Lastrea uliginosa. It grows on the 

 boggy heath, and is occasionaDy the companion of the 

 two species which it resembles, but it is a rare plant. It 

 is similar to the Crested Pern while young, in the form 

 of its half-developed fronds, though when fuUy grown it 

 looks more like L. spimcldsa. It has two kinds of frond. 

 The fertile fronds are nearly erect, and form somewhat 

 circular clumps about two or three feet high. The barren 

 fronds are narrower, not so erect, and taper at the 

 summit into a very long narrow form ; the pinnae, too, 



