CHAPTER XXX. 



OPHIOGLOSSALES. 



THE Ophioglossales include three l genera of living plants : Ophioglossum, 

 with ten species as described in Hooker's Synopsis Filicum, though 

 Prantl distinguishes twenty-nine : Botrychium with about six, or according 

 to Prantl fifteen species : and Helminthostachys with only one. The three 

 genera have well-marked characters in common, so that there is no doubt 

 of their natural affinity. The most distinctive 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 of the eusporangiate 

 type, and are without any annulus. There is no early fossil that 

 can be attributed with any certainty to this family, and thus, notwith- 

 standing that the appearance of these plants is commonly held to 

 be archaic, there is no direct evidence of any great antiquity. They 

 have usually been classed with the Ferns, of which thay have been 

 held to be an outlying group. Other authors recognise certain 

 characters as linking them with the Lycopodiales. A careful consider- 

 ation of the evidence leads to the conclusion that they are best in 

 place as an independent phylum of the Ophioglossales, and the justifi- 

 cation of this will appear from the account of them now to be given. 

 Any decision on the point of affinity is closely related to the 

 question whether the organisms constitute an upgrade or a downgrade 

 sequence. In the description which follows the various types of the 

 family will be traced from the simpler to the more complex, and the 

 discussion of their relationships will be left over to the conclusion, 

 when the facts necessary for forming an opinion shall be before the 

 reader. 



1 The foundation of a fourth genus " Sceptridiuvi " has been suggested by H. L. Lyon 

 (Bot. Gas., Dec., 1905). It is based mainly upon embryological detail. I prefer for the 

 present to suspend any decision as to the validity of this proposal, awaiting the detailed 

 statement of the facts. 



