LASTREA. 97 



Of the Lastreas, seven or eiglit British species are 

 usually recognized, the number varying according to the 

 value put upon certain differences in the plants by different 

 authors. 



The name Lastrea commemorates a zealous botanist 

 and microscopical observer, J\l. Delastre, of Chatelleraut. 

 It is often incorrectly written Lastrcva. 



Lastrea Thelypteris, Presl. 



The Marsh B udder Fern. (Plate VI. fig. 1.) 



This is called the Marsh Fern from its growing in 

 marshes and boggy situations. It has a slender, exten- 

 sively creeping caudex or stem, which is usually smooth 

 and of a dark colour, producing matted fibrous roots. The 

 annual fronds, produced about May, and perishing in the 

 autumn, usually grow about a foot high, the fertile ones 

 taller ; but sometimes, when the plants are vigorous, they 

 reach the height of two or three feet. They are of a 

 delicate texture, pale green in colour, lanceolate, and 

 pinnate. The pinnae are mostly opposite, a short distance 

 ajmrt, and pinnatifidly divided into numerous crowded, 

 entire, rounded lobes. The lobes in the fertile fronds 

 appear narrower and more pointed than those of the 



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