THE YOUNG SPOROPHYTE 



73 



be said to be concentric, it nevertheless approaches closely the collateral type of 

 the other Ophioglossaceae. 



The fusion of the two leaf traces to form the single axial bundle in the basal 

 part of the internode is very much Hke that found in the young sporophyte of Bo- 

 trychium (fig. 49, D, F). The endodermis of the two bundles becomes continuous 

 arid there may be seen intermediate stages of a single bundle, oval in section, but 

 with two conspicuous xylems, separated by the mass of large, thin-walled tissue 

 which gradually disappears as the bundle is followed downward; and finally, in the 

 lower part of the internode, the section of the stele appears quite circular, the center 

 being occupied by the solid xylem formed by the complete coalescence of the xylems 

 of the fused leaf traces (fig. 49, J). The arrangement of the phloem, pericycle, and 

 endodermis is the same 



as in the single leaf trace 

 in the upper region of the 

 internode. 



The base of the stip- 

 ular sheath can be fol- 

 lowed downward to about 

 the level where the two 

 leaf traces begin to coal- 

 esce. Its anterior free 

 portion, between which 

 and the internode is a 

 narrow slit, finally be- 

 comes quite free and its 

 section is visible as an 

 oblong mass of cells lying 

 quite separate from the 

 section of the internode. 



Longitudinal sections 

 of a somewhat older sporophyte are shown in fig. 48, A, B; the third leaf is pretty 

 well developed, with the stipular sheath completely overarching the stem apex and 

 the fourth leaf, which already is conspicuous. The third leaf is still completely 

 covered by the large stipular sheath of the second leaf, which apparently forms a 

 closed cavity, but an examination of the adjoining sections showed that the ante- 

 rior margin of the sheath is quite free in front and that there is a narrow cleft 

 between it and the internode. The real nature of the sheath and its relation to the 

 leaf base is very clearly shown in the median section of the terminal bud from an 

 older plant (fig. 48, C, D), and the resemblance to the terminal bud of Botrychium 

 lunaria, except for the dorsiventral arrangement of the parts, is most striking. This 

 is equally marked in the adult sporophyte, as Farmer has already pointed out. 



The specimen under consideration differed somewhat from the younger one 

 that was described in the relation of the young organs. The cotyledon was better 

 developed and although the lamina was rudimentary the stipular sheath was large 

 and inclosed the base of the second leaf, while in the younger specimen discussed 

 no sheath was developed at the base of the cotyledon. There was a different rela- 

 tion of the roots also, probably associated with the greater development of the 

 cotyledon in the specimen under consideration. The second root, instead of being 

 formed at the base of the third leaf in the terminal bud, was developed a short dis- 

 tance above the cotyledon, near the base of the second leaf, while in the younger 

 specimen no root was developed above the primary root until the third leaf had 



Fig. 5a 



Two sections of the vascular bundles from the series of Helminthoslachys shown in 

 fig 49, showing junction of two leaf traces to form central stele, en^ endoder- 

 mis. X150. 



