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New hybrids in Dryopteris 



Ralph Curtiss Benedict 



Fern students in the eastern United States can hardly expect 

 to find new species in so well-known a region but the discovery 

 that certain native species may hybridize, and that under favorable 



conditions they do so rather frequently, as in the case of Dry- 

 opteris cristata x marginalis^ opens up a field for study which is as 

 yet very little known. There is always the chance that a n^v^ 

 one may be found, and there are problems connected with the 

 variation and the reproduction of the known hybrids which are 

 yet to be worked out. The subject is not a simple one. Indeed 

 a thorough knowledge of the plants can be obtained only after 

 much experimental research and laboratory investigation, but field 

 observers can render service by collecting these plants and record- 

 ing the facts of their distribution, habit, and habitat. Further- 

 more, the intensive study needed in identifying the hybrids will 

 - add greatly to our knowledge of the parent species. 



The hybrids so far reported for eastern United States number 

 eleven and are comprised in three genera. Asploiium has two, 

 A. Ruta-rmtraria x Trichomaites, and the bigeneric hybrid A. 

 platyneuroii x Camptosorus rhizophyllns {Aspleriium ebenoides 

 Scott). The latter is especially interesting as the first of our 

 native hybrids to have its origin experimentally demonstrated.* 

 The remaining hybrids are found in the genus Dryopteris^ which, 

 in this region, contains six species whose habitats are frequently 

 associated, and which seem to hybridize more or less readily with 

 each other. The species are Dryopteris CUntoniana, D, cristata^ 

 /?. Goldiana, D, intermedia, D. margiualis^ and D. spinidosa. 

 Given six units, the number of possible combinations, taking two 

 at a time, is fifteen, and we may expect to find that number of 

 hybrids in this group. The following diagram, adapted from one 

 used by Dr. Ezra Brainard in his studies of violet hybrids, shows 



*Bull. Torrey Club 29 : 487-495. /. 7-7. 1902. 



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