ORIGIN AND RELATIONSHIPS OF THE EUSPORANGIATAE 215 



the cylindrical bundle, or siphonostele, is not due to the formation of a pith within 

 a protostele is clearly shown by the study of the development of the bundle in the 

 young sporophyte oi Botrychium, where it can easily be seen that the component 

 bundles are separate at first, and that the pith, so-called, of the siphonostele is merely 

 a portion of the ground tissue that is included between them, and which later be- 

 comes entirely separated from the cortical tissue. A similar condition of things may 

 be found in tracing the development of the vascular cylinder in the young stem of 

 Helminthostachys. The development of the young bundles in Angiopteris is more 

 like Botrychium than Ophtoglossum, and this, in connection with the separate 

 sporangia that occur in Angiopteris, suggests that perhaps the type of the Marat- 

 tiaceae represented by Angiopteris may have originated independently from forms 

 like Helminthostachys, instead of having had the same origin as those forms in 

 which true synangia are developed. 



The essential similarity of the leaf structures throughout the Ophioglossaceae 

 is sufficiently clear, and the steps in the increasing complexity of the sporophyll can 

 be easily traced in existing forms, ranging from the undivided fertile and sterile 

 segments of Ophioglossum to the decompound leaves and much-branched panicle 

 o{ Botrychium. Helminthostachys is much the most aberrant of the Ophioglossaceae 

 and in many respects shows a marked resemblance to the Marattiaceae. The form 

 and venation of the leaves strongly recall Dancea or Angiopteris, except that the 

 leaves are not pinnately divided, in which respect they closely resemble Botrychium. 

 It must be remembered, however, that the ternate form of leaf characteristic of 

 Botrychium and Helminthostachys is very generally met with in the early stages of 

 the sporophyte in the Marattiaceae. The anatomy of the leaf in Helminthostachys 

 very closely resembles that of the Marattiaceae, there being a well-developed pahsade 

 layer in the mesophyll, a character which is either wanting entirely or very imper- 

 fectly developed in Botrychium. 



The leaves of the Marattiaceae, except in Kaulfussia, in their form and in the 

 circinate coiling of the young leaves, suggest a relationship with the leptosporangi- 

 ate ferns rather than with the Ophioglossaceae. However, the larger species of 

 Botrychium and Helminthostachys show an approach to this circinate form of the 

 young leaf, this being especially conspicuous in the young sporophylls oi Botrychium 

 virginianum. With the exception of Kaulfussia, the general form and venation 

 are alike in all the Marattiaceae and have their nearest analogy in Helminthostachys. 

 There seems no reason to assume that the stipular sheath in the Marattiaceae is dif- 

 ferent in its nature from that of the Ophioglossaceae, especially Helminthostachys 

 and Botrychium. The ternate form of the leaf may be persistent in Kaulfussia, 

 where, however, the venation is more like that of Ophioglossum. Whether this 

 occurrence of both reticulate and pinnate venation in the two families is a case of 

 parallel development, or whether it indicates the connection of the families at dif- 

 ferent points, it is at present impossible to say. 



In the structure of the roots the Marattiaceae find their nearest ally in Hel- 

 minthostachys, where the number of the xylem rays, four to seven, equals that of 

 Kaulfussia, which has the simplest structure among the Marattiaceae, and, as we 

 have seen, probably on the whole is most nearly related to them. Helminthostachys 

 also resembles the Marattiaceae in the character of the apical growth of the root, 

 where, although there is a single apical cell, such as occurs in the young roots of the 

 Marattiaceae, its form is more like that of the Marattiaceae than it is like that of 

 Botrychium. The endophyte which occurs in the older roots of the Ophioglossaceae, as 

 well as in the primary one, I have not found in the older roots of the Marattiaceae, at 

 least not as a regular thing, although it seems to be always present in the primary root. 



