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articulation exists : in Polypodium vulgarc the joint is at the junction 

 of the stipes with the rhizoma, and I find that every discoloured frond 

 in my little city fernery falls off at the slightest touch, leaving a round 

 scar on the rhizoma. In Woodsia the articulation is higher up in the 

 stipes, the disjunction always leaving a portion thereof attached to ihe 

 rhizoma. In Lastraa Callipteris the stipes is long-persistent, its un- 

 derground portion living many years ; there is no trace of articulation, 

 and separation can only be produced by force. A contrast is often 

 produced in the habit of a .species by the character of its rhizoma : 

 thus we see the fronds of Lastra^a multiflora arranged regularly round 

 a centre, w^hile in Lastrsea spinosa they are without arrangement : the 

 cause is to be found in the vertical position of the rhizoma in one, its 

 horizontal position in the other. Who that is aware of this remarka- 

 bly constant distinction could by any possibility confound the species ? 

 In vernation the observant eye will detect great differences, and in no 

 group is this more strikingly displayed than in Pteris, as at present 

 restricted. Thus Pteris tremula is circinate, while aquilina and cau- 

 data have a distinct form of vernation. Excepting for the more easy 

 distinguishing of species, I am inclined to consider the form of frond 

 unavailable. 



On contrasting a vertical with a horizontal rhizoma, an articulate 

 with an inarticulate stipes, a circinate with a simply bent vernation, 

 I find great difficulty in drawing any conclusions as regards the pri- 

 mary grouping of ferns : but it is far different with the fructification, 

 which ajjpears to possess points of structural resemblance throughout 

 groups consisting of many hundred species. I am therefore com- 

 pelled to consider the diversity of structure in those organs whose 

 function is the preservation of the individual, as minor or secondary 

 characters ; while the diversity of structure in those organs w^hose 

 destination is the preservation of the kind, are major or primary cha- 

 racters, and in all natural arrangements must take the precedence of 

 the others. 



May w^e not subdivide these primary and secondary characters, 

 and establish subdivisions in each ? For instance, regarding the veins 

 as receptacles, and therefore equal in importance to the receptacles of 

 flowering plants, we cannot fail to observe that the attachment of the 

 capsules is sometimes median, sometimes lateral ; and this appears 

 to me the distinction between Polypodimn and Asplenium as these 

 were formerly understood. Again, the involucre is sometimes pi*esent 

 and sometimes absent ; and it requires much careful consideration 

 before we can arrive at any just decision whether this discrepancy 



