158 HISTORY OF BRITISH FERNS. 



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 a great number of very curious and some very distinct 

 varieties, differing only, however, rather in the form of the 

 fronds than in the fructification. Of these varieties it is 

 deserving of especial mention that they are for the most 

 part perfectly constant under cultivation, although they 

 have, no doubt, originated in aberrations — that is to say, 

 accidental variations, from the original species, which have 

 been perpetuated naturally or by art. It is, moreover, a 

 curious fact, that most of them arc reproduced from spores. 



One of the most beautiful of these varieties is that called 

 crispum, in which, the same outline of frond prevailing, the 

 leafy portion is so much more developed than the midrib, 

 that the margin becomes excessively undulated, giving the 



