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STUDIES IN THE OPHIOGLOSSACEAE— I 



A Descriptive Key to Ophioglossum in the United States 



By Ralph Curtiss Benedict 



The following synopsis is designed to serve two purposes : to 

 express some of the relationships existing between the various 

 described taxonomic units of the genus, and to further the identi- 

 fication of these units. The terminology used is explained in the 

 following generic description. 



Plants small, terrestrial ; the rhizomes small, erect, more or 

 less tuberous; the fronds one to four, herbaceous, consisting of 

 a usually short, cylindric commonstalk, bearing at its summit an 

 entire, oblique or horizontal, linear-lanceolate to reniform, sessile 

 or short-stalked lamina, and a single, usually long-stalked spike, 

 the sporophyl. 



The terminology in the Ophioglossaceae is in a rather unsatis- 

 factory state. Prantl, who has given the genus Ophioglossum a 

 very thorough systematic treatment, used the Latin equivalents 

 for "leaf" and "petiole," and spoke of the sporophyl as "aris- 

 ing from the petiole or base of the lamina." But the lamina and 

 sporophyl seem to be morphologically coordinate, so that this 

 expression is inaccurate. Professor Underwood has used instead 

 of "petiole" the term "common stalk," which, although not 

 altogether satisfying, is at least not misleading, and this expres- 

 sion is adopted here, being used, however, as a single word. 



Morphological studies of the group seem to demonstrate that 

 the structure here called a "frond" is undoubtedly foliar in 

 origin. On this account, the "common stalk" might as well be 

 called a common petiole, but here the analogy ceases, for the 

 vegetative and reproductive structures above certainly do not 

 correspond to the blade or lamina in ordinary fern or flowering 

 plants. Perhaps the best way out of the difficulty would be to 

 coin one or more new terms for the anomalous structures in the 

 family, but this can best be left to the morphologists at whose 

 hands the group needs further study. 



