4 



THE FERN BULLETIN 



its root is a negligible factor in its life. All it seems 

 to need is mere cranny or crevice or bit of shelf as a 

 place for adequate fastening. A knife may be required 

 to detach it, quite unlike the easy separation of a sod 

 or bunch of P. gracilis with its associated bryophytes 

 from the underlying rock. The roots are relatively 

 coarse, strong and wiry, scantily if at all provided with 

 proper rootlets. Where they come in contact with the 

 rock they usually enlarge or flatten, frequently becom- 

 ing more or less discoid at the end, perhaps the result 

 of pressure, but useful in the capacity of hold-fasts. 

 The dense cushion of flattened and wrinkled hairs and 

 scales at the base of the stems is well adapted to con- 

 serve whatever moisture may have collected about the 

 roots, and to retard its escape except by way of trans- 

 piration. The tufted habit, the blue-green color, the 

 thickened or leathery leaf readily inrolling at the edgs 

 when the moisture is diminished, bespeak the true 

 xerophyte. These characters are in marked contrast 

 with the thin texture of the leaves, the palegreen or 

 yellowish green color, the scattered habit of the stems 

 of P. gracilis, in harmony with its mesophytic nature. 

 Then in its relations to light the cliff-brake likes an 

 open, sunny place, as it is a sun-plant, or heliophyte. 



As to the chemical or nutritive relation of these ferns 

 to the rocks with which they are commonly associated, 

 or whether there are any, I have no data at hand to de- 

 cide, nor do I know that it has ever been investigated 

 experimentally. Such should prove a crucial test. That 

 plants have peculiar relations of this kind to soils is 

 generally acknowledged. This is evident from the 

 names applied to plants characteristic of certain 

 habitats, or to their likes and dislikes. Thus we find 

 plants denominated halophilous, or lovers of salt, cal- 

 ciphilous and calciphobous, loving, or dreading and 



