BRITISH FERNS. 



27 



maturity early in summer, and disappear entirely before the 

 winter ; they are fertile only. 



In describing the form of frond, it must be premised that, 

 under the name Dryopteris, I am about to include the P. cal- 

 careum of Sir J. E. Smith, and I do this because I know of no dif- 

 ferences by which I can distinguish them ; and in order to bring 

 the subject fairly before the reader, I shall quote verbatim Sir J. 

 E. Smith's description, and give a figure of one of his specimens, 

 being one of the very fronds on which he founds the species, 



P. calcareum, Smith. " Frond three- 

 branched: branches doubly pinnate, 

 erect, rather rigid: segments obtuse, 

 somewhat crenate. Masses of capsules 

 crowded, finally confluent." — English 

 Flora, iv. 2^. Sir J. E. Smith fur- 

 ther observes, that the rhizoma 

 shorter and less extended than in 

 Dryopteris. " The frond is also more 

 firm and rigid, its stalk more scaly 

 about the lower part. All the three 

 branches upright; smaller than Dryo- 

 pteris, rigid, and not loosely spreading ; 

 masses of capsules more crowded, 

 finally in some degree confluent, and of 

 a brovmer hue." 



Mr. C. C. Babington has pointed out 

 to me another character, which seems to 

 me of more value than either noticed by Smith. Mr. Babington 

 observes — " P. calcareum may always be distinguished from 

 P. Dryopteris by being covered with minute stalked glands, 

 forming to the naked eye a mealy coat over the whole plant. 

 This is never, as far as my observation goes, to be found in 

 Dryopteris." Still, with regard .to this character, I am com- 

 pelled to add, that I can detect it in scarcely a tenth of the 

 fronds which have been shown me as those of P. calcareum. A 

 very obvious character, and one by which the varieties may be 

 more positively and definitely settled, is to be found in the 

 second pair of pinnae. In Smith's Dryopteris, these second 

 pinnae have each a pair of sessile pinnulae at their union with 

 the rachis ; and in the same author's P. calcareum these sessile 

 pinnulae are entirely wanting. 



