68 



THE OPHIOGLOSSALES 



The longitudinal section of the young sporophyte at this time shows that the 

 thick stele of the root bends upward and is continued into the axis, which already 

 is a good deal elongated and has carried up the young leaves, which are separated 

 from each other by conspicuous internodes. The young sporophyte at this stage 

 thus differs strikingly from the corresponding stages in Ophioglossum and Botrych- 

 lum, with their very closely crowded leaves with no appreciable internodes between 

 them (fig. 46). 



A single stele extends through the axis from its junction with the root stele and 

 forks below the insertion of the rudimentary first leaf, one branch passing into the 

 cotyledon, the other continuing upward and forming the trace for the second leaf, 

 at whose base is seated the apical bud. 



Whether in the younger stages, before the development of the second leaf, the 

 vascular system of the young sporophyte would show the' same relations of the steles 

 of the root and cotyledon, as in Botrychtum, remains to be seen; but from the general 

 similarity in the structure of the young sporophytes of the two this is quite likely; 



yet it is possible that the stem apex is 

 more prominent in the early stages of 

 Helminthostachys and part of the stele 

 which is found in the elongated stem 

 may be of cauline origin, although this 

 is hardly indicated by the condition of 

 things in the apical meristem of the 

 youngest sporophytes that were ex- 

 amined. 



The foot is composed of large- 

 celled, thin-walled parenchyma, with 

 no noticeable differences between the 

 inner tissue and that of the periphery. 

 The stele of the root is continued up- 

 ward without interruption into that of 

 the shoot (fig. 46, B). Probably at an 

 earlier period there would have been, 

 as in Botrychtum, simply the continu- 

 ous stele of the root and cotyledon. 

 At the junction of the root stele with 

 that of the axis there is a marked en- 

 largement, and the short, somewhat ir- 

 regular tracheids are decidedly broader 

 than those either in the root or in the portion of the stele above the junction. The 

 tracheids toward the outside of the central region are slender and have delicate 

 reticulations, which closely approximate the form of true spiral thickenings. These 

 are the protoxylem elements and can be traced upward and downward into the 

 stem and root, respectively. The secondary tracheary tissue is marked by broad, 

 reticulate thickenings, and these in the largest tracheids are replaced by conspicu- 

 ous oval or nearly round bordered pits, very much like those which are found in Bo- 

 trychtum (fig. 46, E). 



Above the base of the root there is a long internode below the cotyledon, and 

 through this runs the single axial stele. On the same side of the axis as the primary 

 root may be seen the cotyledon, which closely resembles in form the young cotyledon 

 of Botrychtum virgtntanum, but instead of developing into a functional leaf it is 

 arrested in its growth before the lamina is fully developed. As in the cotyledon of 



pr... 



Fig. 45. 



A. Young sporophyte of Helminthostachys, attached to gameto- 



phyte, pr. co/, cotyledon; f-^, r^, first and second roots. X 2. 



B. Leaf from an older sporophyte. Xl. 



