CHAPTER XXXI. 



COMPARATIVE DISCUSSION AND SUMMARY FOR THE 

 OPHIOGLOSSALES. 



THE Adder's Tongues cannot yet be considered as located in a definil 

 position in relation to other groups of Pteridophytes. Their tradition; 

 place among the Ferns was accorded to them somewhat light-heartedly, am 

 before the details of their anatomy or development were adequately knowi 

 They share two external characters with the Ferns, viz. that they are large 

 leaved, and that the sporangia are distributed over a considerable extei 

 of the foliar organ. But to use these in themselves as a ground for ranking 

 them as Ferns involves the assumption that the origin of a large sporoph] 

 only occurred once in Descent, an assumption that is not warranted. Oi 

 the other hand, a relationship with the Lycopodiales has been ascribed 

 them : this has been based in the first instance upon the position of theii 

 peculiar spore-bearing member, the spike, as it is called; and it has 

 urged that the insertion of this part is the same as that of the sporangiui 

 of the Lycopodiales or of the sporangiophore of the Psilotaceae, while tl 

 function of these parts is also alike. This argument, like the first, 

 its cogency from an assumption, that all the appendages holding a venti 

 position on the leaf were of common origin. But parallel development ii 

 distinct phyletic lines may account for this common feature, as it doe 

 for so many others in the plant-body. The day is past when single 

 characters such as these can be accepted as defining relationships, and 

 is in the study of all the characters that an indication of the natun 

 position of any family is to be found. Certain recent writers have indicate 

 a specially primitive position for the Ophioglossaceae, comparing them directb 

 with the Anthocerotales, 1 while V. Wettstein 2 gives them the first positioi 

 in his treatment of the Pteridophyta, with the remark that "the Ophic 

 glossales are the only living Pteridophytes from which the rest of the 

 Pteridophytes can be derived." With such divergent opinions before 



1 Campbell, Mosses and Ferns, 1905, p. 600. 

 - Handbuch d. Syst. Bot., p. 52, etc. 



