DRYOPTERIS BORRERI NEWM. IN THE BRITISH ISLES 



65 



Summary 



(1) The characteristics of D. horreri Newm. are given. 



(2) All the existing records of the occurrence of D. horreri in the British Isles 



are presented on a map and a list is given of herbarium specimens. 



(3) Von Wolf's map showing the northern limits of D. horreri in Europe is 



reproduced : the occurrence of this species throughout the British Isles 

 (except the Shetland Islands) agrees very well with its distribution on the 

 continent. 



(4) The scarcity of this fern in some parts of the British Isles is discussed and 



accounted for mainly by the lack of distinction from D. filix-mas by 

 collectors. 



(5) D. horreri seems to prefer damper and shadier situations than D. filix-mas. 



(6) Some points which may be clarified by cytological work now being undertaken 



are mentioned. 



I am most grateful to the Trustees of the British Museum (Natural History) for 

 a vacation studentship; to the keepers or owners of the herbaria listed above for lending 

 material for inspection; to the staff of the European and Cryptogamic Herbaria at the 

 Museum for much help; and especially to Mr. Alston, without whose help this work 

 would not have been carried out. 



REFERENCES 

 LEE, J. R., 1933, The Flora of the Clyde Area. 



MANTON, I., 1950, Problems of Cytology and Evolution in the Pteridophyta. 

 NEWMAN, E. , 1854, A History of British Ferns. 



WARBURG, E. F., 1952, in CLAPHAM, A. R., TUTIN, T. G. and WARBURG, E. F., Flora of the 

 British Isles. 



VON WOLF. 1936, Ein neuer Earn der Pfalz, sein Vorkommen und seine systematische Stellung, Pollichia, 5. 



