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thallium, developing regularly its single sporophyte, would 

 require more than one season for its growth. It is possible 

 that the more plastic character of Ophioglossum with reference 

 to the influence of light as compared with Botrychium may be 

 an indication of the more primitive character of the genus. 

 Thus in Peirce's experiment Fimbriaria and Gymnogramme 

 are undoubtedly more specialized types than Anthoceros which 

 was much more plastic than the former. This view would also 

 harmonize with the relative behavior of 0. moluccanuni and 

 O. pendulum with respect to the development of chlorophyll in 

 response to exposure to light. The sajDrophytic habit becomes 

 far more marked in 0. pendulum, where the gametophyte 

 reaches a very great size and develops unlimited power of 

 multiplication. This may be assumed perhaps to be connected 

 with its epiphytic habit. 



As has been urged by the writer before (Mosses & Ferns, 

 2d edit., p. 278) the similarity of the sexual organs in 

 Opliioglosswn and the Marattiaceae is very great, and there 

 are also strong points of resemblance to Equisetum, which we 

 are inclined to believe belongs to the same great series as 

 the eusporangiate ferns. The form of both archegonium and 

 antheridium is strikingly similar, and the very large sperma- 

 tozoids of Ophioglossum are more like those of Equisetum than 

 like those of any true fern. Presumably the ancestral type from 

 which Ophioglossum came, had a large green prothallium not 

 so very difterent from that of the Marattiaceae or, possibly 

 may have been a branching green gametophyte like that found 

 in Anthoceros or Equisetum. There might also be considered 

 in this connection the chlorophylless prothallium of Isoetes, 

 whose archegonium and embryo have a certain resemblance 

 to those of the Ophioglossaceae, and whose sperraatozoids are 

 also multiciliate. 



Three types of embryo may be recognized in Ophioglossum 

 represented respectively by 0. moluccanum, 0. vulgatum and 

 0. pendidum. If, as seems not unlikely 0. moluccanum is the 

 most primitive of the three, some interesting points arise as 



