BRITISH FERNS. 



The estimated number of British Lastreas varies according 

 to the value put upon certain differences in the plants, by 

 different authors ; we admit seven to the rank of species. 



The name has been applied in honour of M. Delastre, a 

 zealous French botanist and microscopical observer. 



MARSH BUCKLER FERN. 



This Fern is the Lastrea Tlielypteris of botanists ; and has, 

 among other synonyms, those olAryidium Thelyptcris, Poly- 

 podium Thelypteris, Polystichuth 'Thelypteris, T/ielypteris 

 pcdustris, and Hemestlieum TMypteris. 



This plant is called the Marsh 

 FIG. 8. Fern from its growing in marshes 



and boggy situations. It has a 

 slender, extensively creeping 

 stem, which is usually smooth 

 and of a dark colour, producing 

 matted fibrous roots. The an- 

 nual fronds produced about May 

 and perishing in the autumn, 

 usually grow about a foot high, 

 the fertile ones taller : but some- 

 times, when the plants are vigor- 

 ous, they reach the height of 

 two or three feet. They are of 

 a delicate pale green, lanceolate, 

 pinnate, the pinnae mostly oppo- 

 site, and pinnatifidly divided 

 into numerous entire rounded 

 lobes. The lobes in the fertile 

 fronds appear narrower and more 

 pointed than those of the bar- 

 ren, on account of their margin 

 being rolled in. The venation 

 of the lobes of this Fern con- 

 sists r\ a ^distinct, somewhat 

 wavy inidvein, from which alter- 

 nate usually forked venules 

 branch out, and both branches 

 bear a sorus half way between 

 the margin arid the midvein. 

 The sori often become confluent, 

 and are partially concealed by 

 the bent-back margin. The indusium, or cover of the spore 



Lculrea Thelypterit, 



