THE YOUNG SPOROPHYTE 83 



centric bundles as they occur in the petiole of Helminthostachys and Botrychium 

 must be considered as secondary. The monarch root of Ophioglossum moluc- 

 canum and the other members of the section Euophioglossum is to be considered 

 as a relic of the primary condition where the single axial stele, as in the young spo- 

 rophyte of 0. moluccanum, had the single strand of practically uniform structure, 

 extending through the leaf and root. The development of diarch roots, such as 

 those of 0. pendulum and Botrychium, is probably also secondary and perhaps 

 associated with the early development of the second leaf in these forms. The diarch 

 root appears again in the young sporophyte of the Marattiaceae and is permanent in 

 most of the leptosporangiate ferns. The roots of the larger species of Botrychium 

 and especially those of Helminthostachys, with their increased number of xylems, 

 are undoubtedly secondary developments, perhaps associated with the large size of 

 the roots; and we again find this same type developing in the Marattiaceae. In 

 regard to this point, Helminthostachys is the most aberrant of the Ophioglossaceas 

 and approaches nearest to the Marattiaceas. 



The leaf in the smaller species of Ophioglossum is probably a very primitive 

 structure and the closed stipular sheath — which is not exclusively foliar in origin, 

 but at first owes part of its tissue to that of the cortex of the root, from which the 

 sporophyte arises — is probably an older structure than the strictly foliar, stipular 

 sheaths in Botrychium and Helminthostachys. The simpler types of Botrychium, 

 like B. simplex and B. lunaria, show a transitional condition between the closed 

 sheath of Ophioglossum and the open sheath oi B.virginianum,'whic\\ may really 

 be spoken of as composed of two stipules, in this respect recalling the Marattiaceae. 

 Helminthostachys, in the development of the stipular sheath, agrees exactly with 

 the simpler types of Botrychium. In these forms the sheath is hood-shaped, open- 

 ing by a transverse slit in front and below, and the upper portion of the sheath is 

 broken through when the inclosed leaf emerges, so that the two apparent stipules 

 in Helminthostachys are really secondary, caused by a tearing of this hood-shaped 

 sheath, and are not proper stipules as they are in Botrychium virginianum. 



The simpler and probably more primitive species of Botrychium, like B. 

 simplex and B. lunaria, are obviously intermediate between Ophioglossum and 

 the larger and more specialized species oi Botrychium. This is shown in the form 

 and venation of the leaves, as well as in the character of their tissues. Instead of the 

 pinnate venation found in the leaves oi B. virginianum, these more primitive species 

 show no midrib in the leaf, but the veins all radiate from the veins of the leaflet, 

 dividing dichotomously, so that they are arranged in a fan-like fashion. Were the 

 ends of the veins connected there would result a reticulate venation, exactly like that 

 of Ophioglossum. These leaves, moreover, are fleshy in consistence and have 

 stomata upon both sides, while in Botrychium virgmia'num and in Helminthostachys 

 the stomata are restricted to the lower surface of the leaf. In all of these particulars 

 Ophioglossum and the simpler species of Botrychium are evidently more primitive 

 than the other genera. 



In Botrychium virginianum, as we have seen, the cotyledon is extraordinarily 

 developed, more so than that of any other Pteridophyte. The contrast between 

 this highly developed cotyledon and the very rudimentary one in Botrychium lunaria, 

 where the young sporophyte passes several years under ground before the first green 

 leaf emerges, is very striking. It is, however, to be assumed that the rudimentary 

 condition of the leaves in Ophioglossum vulgatum and Botrychium lunaria is a 

 secondary condition, connected with their long life under ground. 



Helminthostachys, on the whole, approaches more nearly to B. lunaria in its 

 early stages of development than it does to B. virginianum. This is shown in the 



