1902J Davenport, — Notes on New England Ferns, — V 163 



use of Nephrodium as per his citation in Michaux, second the verifica- 

 tion of Moore's citation for N. Fi/ix-mas, and third, a type that is not 

 a Polystichum although Adanson described it as such ("envolucre 

 enparasol.") 



However as Fi/ix-mas is the species upon which Dryopteris is 

 assumed to rest let us briefly consider the relative position of that 

 genus and Nephrodium with regard to it. 



Dryopteris, although derived from the earlier pre-Linnaean name 

 (Druopteris) of Dioscorides, dates from Adanson (1763), Nephro- 

 dium from Richard (1801), and this gives to the name Dryopteris a 

 priority in time. But the name Dryopteris was not used again by 

 any author for more than seventy years after its use by Adanson and 

 this, according to the Berlin Rule 1 which is now accepted by many 

 conservative botanists, relieves us of any obligation- to take such a 

 name up now. Furthermore Adanson's description does not apply to 

 the species mentioned in connection with it, and the result is an 

 incongruous combination, which is not entitled to serious considera- 

 tion. If we put this to a test by analysis we will have some such 

 form as this : — 



Dryopteris: — " ettveloppe enparasoi '" i. e. indusium peltate, with 

 uninterrupted margin, the attachment being strictly central. 



Example: — Fi/ix-mas, indusium cordate-rcniform, i. e. with the 

 margin deeply cleft on one side into a definite sinus with the attach- 

 ment at its base, thus appearing one-sided instead of central. 



Result, a disagreement. 



Now the interpretation of "enparasol" admits of only one mean- 

 ing and it has never had any other than the one which represents a 

 lady's sunshade — a parasol, or an umbrella, and no one has ever 

 known a parasol to have its handle otherwise than m the centre, or 

 to have its rim divided. It is impossible to reconcile the disagree- 

 ment that we have here, and I know of no better characterization for 

 a genus with its description standing for one thing and its type (\) for 

 another than the one I have previously used of being ill-defined. It 

 is not enough to say that Adanson intended to describe Fi/ix-mas, 

 the fact that he did not do so correctly is beyond dispute. Besides, 

 no subsequent author used Dryopteris until Schott, in 1834 (71 years 



1 As this rule, which is known as the fifty year limit, has been much misrep- 

 resented of late, it may be well to explain here that it has nothing whatever to 

 do with species, but applies to genera only. 



