CHAPTER XIX 



OPHIOGLOSSACEAE 



The preceding Chapter has dealt with organisms known only in the 

 fossil state. This Chapter will treat of plants known as living objects. 

 Scott remarks {^Studies, Part i, 3rd Edn., p. 362) that "unfortunately nothing 

 is known of the geological history of the Ophioglossaceae: we are therefore 

 driven to compare directly a recent with a Palaeozoic group of plants," 

 Nevertheless the points of agreement "seem sufficiently to justify the 

 opinion that the Ophioglossaceae have more in common with the Botryo- 

 pterideae than with any other known group of plants. The affinity must, 

 however, be a somewhat remote one." That is the general result of recent 

 comparisons, and it is well to state it in the terms quoted, so as to give at 

 the outset some indication of the view to be developed here from the facts 

 relating to the Ophioglossaceae, or Adder's Tongue Ferns ^ 



The Ophioglossaceae include three genera of living plants : Helmintho- 

 stachys with one species only, Botrychiuin with 34 species in Christ's Index, 

 and Ophioglossum with 43 species. They all have well-marked characters 

 in common, so that there is no doubt of their natural affinity. Their most 

 distinctive feature is the fertile spike, a process which rises from the adaxial 

 surface of the leaf, and serves as a basis for insertion of the sporangia : these 

 are marginal in position upon it; they are of the Eusporangiate type, and 

 are without any annulus. Their individual spore-output is very large. The 

 plants of this cosmopolitan family are all perennials; they are mostly xero- 

 phytic and ground-growing, though some few are epiphytic. The method of 

 their perennation is closely connected with their habit. The shoot is 

 markedly megaphyllous. The stock is usually short, upright, and un- 

 branched. It is buried in the soil, and is attached by thick radiating roots. 

 The leaves, which are always stipulate, are borne in spiral sequence in the 

 upright forms, and as a rule one large leaf is expanded in each season: 

 rising above the soil, it carries out both photosynthesis and spore-produc- 

 tion, and it dies down at the resting season, leaving the stock stored with 

 nutrition for the next year. This is the habit for Botrychiuvi and Ophioglos- 



1 Nevertheless, it may be well to bear in mind the existence of early fossils which have been 

 referred to an Ophioglossaceous, or perhaps with equal claim to an Osmundaceous, affinity : such as 

 Phacopteris paniculifera Stur. (E. and P. i, 4, Fig. 288). The reference rests rather on general 

 habit than on details of structure, or on the propagative organs. Until these are better known, it 

 seems wise to hold any decision in suspense. 



