RARE FORMS OF FERNS - Vll. 



Although the opportunities for hybridizing among 

 ferns are much rarer than they are among 

 flowering plants, hybrid ferns undoubtedly occur. In 

 a few cases, such as that of Camptosorus rhizophyllus 

 X Asplenium ebeneum (Asplenium ebenoides) the 

 hybrid nature of the plant has been proved experi- 

 mentally but in most, the hybridity has been inferred 

 from the resemblance of the new form to its supposed 



Asplenium Trichomanes x Ruta-muraria. 



parents. The latter seems to be the case with the 

 specimen here illustrated, the dark stipe and lower 

 rachis and the shape of the upper pinnae being taken 

 to indicate trichomanes characters while the distant, 

 three-parted lower pinnae, the green upper rachis and 

 the long stipes are held to be characteristic of ruta- 

 muraria. 



Until about three years ago, this plant was not 

 known to be a member of our fern flora. In 1905 Mr. 

 G. A. Woolson found it near Proctor, Vt, growing 

 within three feet of Asplenium ruta-muraria and not 

 very far removed from A. Trichomanes. The plant 

 had previously been known from Europe and was given 

 the name it bears by Ascherson and Graebner in 1S9G. 

 Dr. Christ figured it in "Die Farnkrauter der Schweiz," 

 but since hybrids are likely to vary considerably it is 

 desirable that an illustration of the American form be 



4G 



