THE CLASSIFICATION OF FEIINS. 47 



the most important additional cliaracteristic called into 

 requisition being that derived from the presence or absence 

 of a general investing membrane or cover to the spore-cases, 

 and its form, origin, and mode of bursting when present. 

 Tliis, in fact, brings us to the basis of the classification 

 which has prevailed till witliin comparatively very few 

 years, and even, to some extent, up to the present time. 



Another feature has, however, latterly been adopted by 

 many botanists skilled in the knowledge of Ferns, as form- 

 ing the leading characteristic of their family relationship, 

 the groups thus brought together representing the modern 

 classification of Ferns. The feature thus adopted, as 

 affording the marks of family recognition, is the veining 

 of the fronds. This character, as employed at the present 

 day, in conjunction with the characters derived from tho ' 

 clusters of spore-cases and their covers, leaves but little 

 scope for further improvement. The tendency of the sys- 

 tem is, however, towards subdivision of the family groups, 

 and in this direction it is perhaps somewhat lirble to err. 



