FERNS OP GREAT BRITAIN, 41 



frond' lias a much more vigorous appearance than the 

 barren one. The latter appears in May, and the fertile 

 frond in July. 



Each lobe of the Marsh Fern has a somewhat winding 

 mid-vein, from which the side veins branch alter- 

 nately, and the clusters of fructification are seated 

 on both branches, half-way between the mid-vein and 

 the margin. The clusters are abundant, and in an early 

 stage of the plant the thin, white, membrane-lite indu- 

 sium may be seen ; but as the capsules increase in size 

 it disappears. The fronds of this species are not so 

 tufted as some others, but spring up, at intervals, from 

 the long slender underground stem. The plant is 

 classed by various writers in the genus Polypodium 

 Acro'stichum or Poli/stichum ; but it always retains its 

 specific name of Thel'ypteris. Mr. Newman terms it 

 JSemestheum Theli/pteris. 



2. L. Oreopteris (Heath Fern, or Sweet Mountain 

 Fern). — Fronds tufted, pinnate ; pinnce pinnatifid ; fruc- 

 tification marginal. This species resembles the last in 

 so many of its characters that it has often been mistaken 

 for it ; but when growing, it has a very different aspect 

 on the landscape. Its fronds, instead of rising here and 

 there at distance? from each other, spring up in almost 

 circular tufts, and are usually two or three feet high ; 

 the stalk is very short, and covered with pale brown 

 scales, while in the Marsh Fern it is smooth. As its 

 famihar name would indicate, this fern grows on exposed 

 and mountainous places, on heaths and dry pastures, 

 and is found, though less frequently, on open or wooded 

 lowland districts. On some waste lands, as those of 



