THE FERN BULLETIN 



3 



doubtless the implication when they are discussed in 

 their preferential relations to limestone or sandstone. 

 It would seem to apply in but a very general way to 

 P. gracilis. In the strict sense of the term it is not a 

 lithophyte, or plant closely connected with a rock sub- 

 stratum. At least I do not find any connection be- 

 tween its roots and the underlying rock, however 

 otherwise, if at all, they may be related. The roots 

 may casually pass through the thin stratum of soil in 

 which it grows and thus come in contact with the rock, 

 but they show no adhesive nature. The rocks provide 

 a lodging place for this layer of soil in which it takes 

 root and shelters the delicate fronds from adverse 

 conditions. The roots spread in a medium well sup- 

 plied with humus They are fine, with abundant fibers 

 and root hairs for the absorption of nourishment. Be- 

 sides it is usually associated with mosses, liverworts 

 and other small plants adapted to such a habitat. 

 These are its edaphic features and relations as I have 

 found them, and from the character of its root-system, 

 it would require essentially the same conditions any- 

 where. In its relations to moisture it is a mesophyte, 

 since it demands a moderate supply of water. The 

 locality may become dry in late summer from heat or 

 lack of rain, but as it fruits in early summer its season 

 of activity is over, the aerial parts may wither and dis- 

 appear, and the tiny fronds be hard to find. In its re- 

 lations to light it is a sciophyte or shade-plant. It is 

 to be sought on shaded rocks, since the direct rays of 

 the sun, which the common cliff-brake readily endures, 

 are detrimental, or might prove fatal. 



It is quite different in the case of P. atro purpurea. 

 It is true xerophyte, capable of living under the dry- 

 est of conditions. It is doubtless a good lithophyte, 

 since any soil but the rock itself that may be found at 



