X. SCOLOPENDRIUM. 177 
cases arise from separate but adjacent fascicles of veins, 
one being attached to the upper side of the anterior brancli 
of one, and the other line to the lowest side of the posterior 
branch of the next fascicle, and so on over the fertile 
portion which generally occupies three-fourths of the frond. 
They are each covered with a pale-coloured membranous 
indusium, which is so attached, that the free margin is 
exterior as regards the fascicle of veins to which it is at- 
tached; and, though at first touching each other, and 
opening therefore in opposite directions like a pair of fold- 
ing doors, they are soon pushed back by the growing 
masses and lost, the double series of spore-cases becoming 
so united as to form one crowded line. The son are of 
very unequal length. 
There are numerous varieties of this fern, nearly all of 
which are more or less monstrous in their development. 
They are, however, for the most part very constant, and 
hence as they are really very different in their aspect, 
this species is one of the most valuable to the cultivator. 
The variety polyschides, has the fronds six inches to a 
foot long, narrower than the common form, somewhat 
pinnatifid, and deeply and irregularly crenately-lobed on 
the margin; they are erect, and when very luxuriant 
have a little tendency to undulation, and are more. or less 
fertile. The sori are short, oblong, or linear, very irregular. 
The variety marginatum, is the most remarkable and 
the most beautiful of all the forms as yet known. The 
fronds grow erect, a foot or more in height, and stand in a 
circle around the crown ; they are simple strap-shaped, the 
margin irregularly lobed, the under surface producing 
within the margin an excurrent membrane which is also 
lobed. Both surfaces of this membrane and the under 
surlace of the frond itself exterior to it are soriferous. 
The fronds have therefore as it were a double margin. In 
the less perfectly developed condition, the membrane is 
reduced to the form of a longitudinal vein-like ridge. This 
variety was first found near Nettlecombe, in Somerset- 
