166 HISTORY OF BRITISH FERNS. 



ment, dependent on the circumstances in Avhich it grows. 

 Its more usual size is from three to four feet in height. 

 Sometimes in dry, very sandy soil, the plant becomes a 

 pigmy, not reaching a foot in height, and being merely 

 bipinnate. The opposite extreme occurs when the plant 

 is growing on damp hedge-banks, in warm shady lanes, 

 where it attains eight or ten feet in height, and is 

 proportionately compound in its development. Under 

 circumstances which favour the most luxuriant deve- 

 lopment, this common and usually vulgar-looking plant 

 combines the most noble and graceful aspect, perhaps, 

 which is borne by any of our indigenous species, its 

 fronds scrambling up among the bushes, which sustain 

 them at the base, while their graceful feathery-looking tops 

 form, overhead, a living arch of the tenderest green. 



The Pteris is known among our native Ferns by having 

 the edses of all the little divisions of its fronds furnished 

 with a line of spore-cases. No other of our native species has 

 the fructification arranged in continiious lines except this 

 and the Blechnum ; and the Pteris may be readily known 

 from that by the lines being in it confined to the margin, 

 leaving the centre unoccupied, while in Blechnum the 

 extreme margin is unoccupied by the sori. 



