LASTREA. 
97 
Of the Lastreas, seven or eight 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, M. Delastre, of Chatelleraut. 
It is often incorrectly written Lastrwa. 
Lastrea Thelypteris, Presl. 
The Marsh Buckler 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 
apart, and pinnatifidly divided into numerous crowded, 
entire, rounded lobes. The lobes in the fertile fronds 
appear narrower and more pointed than those of the 
H 
