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ABNORMAL FORMS, AND HYBRIDITY IN FERNS* 



NE of the most interesting forms of variation is found in 



the fronds of dimorphous ferns, i. e. ferns with two kinds 



of fronds, where we meet with many strange phenomena 

 for which satisfactory explanations are not always readily avail- 

 able. In what we might call semi-dimorphous ferns, that is, in 

 those ferns which like the Anemias and Botry chitons, and we 

 might include here Osmunda regalis, have their fertile and ster- 

 ile portion borne on separate stalks, but with one common foot- 

 stalk, we find some curious transitional states occurring. Some- 

 times the fertile panicle is partially sterile with lamina-like divi- 

 sions, and sometimes the sterile portion is sporangiferous with 

 more or less scattered sporangia, in some cases even whole divi- 

 sions being transformed into fruit. 



Among the strictly dimorphous ferns some of the Acrotti- 

 c hunts show remarkable transitional states in which the fertile and 

 sterile portions become mixed up in all sorts of ways, and I take 

 it that all dimorphous ferns are likely at some time or other to 

 exhibit similar traits of character. The frondosa forms of Os- 

 munda cinnamomea will no doubt suggest themselves to you at 

 once and it is those forms, and the obtusilobata form of Onoclea 

 sensibilis, that I am going to speak about especially, not only be- 

 cause of their furnishing examples near home with which you are 

 likely to be most familiar, but because there are still some open 

 questions as to the causes which produce them. 



It is a little singular that while Osmunda regalis frequently 

 produces abnormal variations, Osmunda Claytoniana seldom 

 does so. But O. cinnamomea frequently, and, in some cases 

 without any apparent cause, produces transitional fronds which 

 are partly fertile and partly sterile ; these transitional fronds be- 

 ing, as is the case with other ferns of this class, what should 

 otherwise be fertile fronds.* Sometimes these transitional fronds 

 simulate the fertile fronds of O. Claytoniana, having fertile pinnae 

 in the middle of the frond with sterile pinnae above and below, 

 although we never find Claytoniana simulating or approaching 



By Geo. E. Davenport. 



* According to Rev. Dr. Campbell in Canadian Horticultural Magazine 

 for Sept., 1898, the frondosa form is as common in Province of Quebec as the 

 normal form of the species itself. 



