CHAPTER XXxXI. 
COMPARATIVE DISCUSSION AND SUMMARY FOR THE 
OPHIOGLOSSALES. 
Tue Adder’s Tongues cannot yet be considered as located in a definite 
position in relation to other groups of Pteridophytes. Their traditional 
place among the Ferns was accorded to them somewhat light-heartedly, and 
before the details of their anatomy or development were adequately known. 
They share two external characters with the Ferns, viz. that they are large- 
leaved, and that the sporangia are distributed over a considerable extent 
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 sporophyll 
only occurred once in Descent, an assumption that is not warranted. On 
the other hand, a relationship with the Lycopodiates has been ascribed to 
them: this has been based in the first instance upon the position of their 
peculiar spore-bearing member; the spike, as it is called; and it has been 
urged that the insertion of this part is the same as that of the sporangium 
of the Lycopodiales or of the sporangiophore of the Psilotaceae, while the 
function of these parts is also alike. This argument, like the first, draws 
its cogency from an assumption, that all the appendages holding a ventral 
position on the leaf were of common origin. But parallel development in 
distinct phyletic lines may account for this common feature, as it does 
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 it 
is in the study of all the characters that an indication of the natural 
position of any family is to be found. Certain recent writers have indicated 
a specially primitive position for the Ophioglossaceae, comparing them directly 
with the Anthocerotales,! while V. Wettstein® gives them the first position 
in his treatment of the Pteridophyta, with the remark that “the Ophio- 
glossales are the only living Pteridophytes from which the rest of the 
Pteridophytes can be derived.” With such divergent opinions before us 
+Campbell, Mosses and Ferns, 1905, p. 600. 
? Handbuch d. Syst. Bot., p. 52, etc. 
