THE LITERATURE OF FERNS. 47 



the pages of the best English and American 

 magazines. But the absence of subject-catalogues 

 renders this literature practically useless. Chance 

 may direct us to what we are looking for ; but, 

 until our principal libraries shall put into practice 

 some index-system which shall give to us control 

 of these writings, many of them will be lost, and 

 they are liable to be unintentionally reproduced 

 by other authors in after-years. 



