SCOLOPENDRIUM. 171 



one the other ; the free margin, therefore, is exterior with 

 reference to the fascicle of venules to which it belongs. 

 When very young there is no evident trace of separation at 

 the part where they overlap, but as they advance towards 

 maturity the separation becomes apparent, and they even- 

 tually open down the centre, one indusium turning upwards 

 and the other downwards, the two lines of spore-cases 

 they had covered becoming confluent and undistinguishable 

 without manipulation. 



This is the ordinary form of Scolopendrium ; but there are 

 some very curious and distinct varieties, differing only, 

 however, in the form of the fronds, and not in the fructifi- 

 cation, where it is present. Of these varieties it is deserving 

 of especial mention that they are perfectly constant under 

 cultivation, although they have, no doubt, originated in 

 aberrations, that is to say, accidental variations of the ori- 

 ginal species, which have been perpetuated either naturally 

 or by art. 



The most beautiful of these varieties is that called cris- 

 pum, in which, while the same outline of frond prevails, 

 yet the leafy portion is so much more developed than the 

 midrib, that the margin becomes excessively undulated, 

 giving the fronds a very elegant curled or crisped ap- 



