FERNS. 121 



bundle hardly falls within the scope of an elementary 

 course. 



RELATIONSHIP. 



A careful comparative study of a number of prominent 

 genera of ferns should be made. Those named above are 

 widely distributed, and, in general, easily procurable. For 

 this part of the work, dried specimens are nearly or quite 

 as satisfactory as fresh ones. The comparison, while in- 

 cluding a study of external characters, should be directed 

 primarily to the fructification, which presents the really 

 distinctive features of the different genera. It is necessary 

 in each of the genera studied, to observe particularly the 

 form of the sorus and indusium, and the way in which the 

 latter is attached to the leaf. If ten or a dozen different 

 kinds of ferns are studied in this way, with accompanying 

 drawings and descriptions, the student will have learned 

 from his own observation the salient characters of the 

 ferns as a group, the marks that distinguish the more 

 prominent genera, and the features by which the species 

 belonging to them are recognized. 1 



The ferns include three thousand or more species, vary- 

 ing widely among themselves in habits and external feat- 

 ures. With leaves of extraordinary variety and beauty ; 

 their texture delicate or coriaceous, or extremely thin and 

 translucent, as in the filmy ferns ; of various habits, creep- 

 ing, climbing, erect, or tree-like ; growing in every quarter 

 of the globe, and yet exhibiting marked preferences of soil 

 and surroundings ; a dominant group in earlier geological 

 time, and still holding a manifest supremacy among the 

 higher cryptogams, they present themselves as one of the 

 most varied and attractive, and at the same time most easily 



1 For further hints see Underwood, Our Native Ferns and their Allies. 



