RARK LOCAL FERNS. 35 



But it is safe to say that the eleven localities credited to Dela- 

 ware county could easily be quadrupled. This species grew 

 most luxuriantl}^ at Castle Rock for many years, and probably 

 would grow there yet but for the lamentable destruction of 

 that famous place through the short-sighted greed of a corpo- 

 ration. Thence down Crum creek, almost wherever fitting 

 conditions obtain, it is to be seen in more or less abundance. 

 So, also, along Uarby, Ridley and Chester creeks, down to the 

 i8o foot contour line, it may be discovered by the trained eye 

 in many places. But the eye must, for best results, be trained 

 not only to see the plant itself, but also to recognize the char- 

 acteristics of a probable habitat. The fern demands for its 

 growth and welfare a rock that is not too dry, not too much 

 exposed to direct sunlight ; and in most instances it is the 

 north side only of the rock that is occupied, though in certain 

 cases the fern grows well upon the very top, among grasses 

 and weeds. When this happens, however, the rock is in a 

 place overshadowed by trees. The kind of rock seems to 

 matter verv' little, provided it be not too new and bare. On 

 limestone the fern absolutely riots. On serpentine, as at the 

 Black Rocks locality on Mill creek near Biyn Mawr, it was 

 for many years scarcely less luxuriant. On serpentine, near 

 Media, it does excellently well. For the rest, there are the 

 igneous masses of Castle Rock and the gneissic hugeness of 

 Mount Miser\', at Rockdale. In no place is the species more 

 at home than in that last mentioned, and nowhere else does it 

 present more of those sports and oddities of form which indi- 

 cate a condition of prosperity that has lifted it above the stern 

 warfare of life and given the wherewithal to try experiments. 

 But nowhere does the walking leaf wax wanton, nowhere does 

 it really seem happy or contented, or even well conditioned, 

 save where there is something more for it to grow in than a 

 mere crack in the face of a rock. There must be retained 

 moisture, some little dark woods earth, some humus. -^More- 

 over, it is frequently crowded out, as the years elapse, b}^ that 

 coarse barbarian, the rock polypod. 



