THE STRUCTURE OF PERNS. 11 



or beneath the surface of the soil, and forms what is called 

 a creeping stem. These creeping stems are generally 

 clothed with hairs or scales, and sometimes to such an 

 extent as to become quite shaggy ; they vary greatly in size, 

 some being as thick as one's wrist, and others, as in our 

 native Hymenopliyllums, as fine as threads. 



The common Polypody has the thickest stem of any 

 of the creeping British species : in this it is about as thick 

 as one's thumb ; but that of the common Bracken, or Pleris, 

 creeps the most extensively. The Osmuncla, or Flowering 

 Pern, as it is called, is, of the native upright-growing species, 

 that which most readily gains height, and very old plants of 

 this may sometimes be found with bare stems of a foot or 

 more in length. The common Male Pern, the Lastrea Oreop- 

 teris, and the Polystichum angnlare, have also a tendency, 

 though in a less degree, to this mode of growth, but it never 

 becomes apparent except in the case of very aged plants. 



The leaves of Perns are generally called fronds, and as we 

 think this latter term the most appropriate, we shall adopt 

 it, with this general explanation, that it means the leaf-like 

 organs which are borne on the proper stem. The leaf-like 

 character they bear, has led some botanists to reject the 

 term frond altogether, and to consider them as true 



