. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. Fig. 48. A, B. Two sections of terminal bud of a young sporophyte of Helminthostachys. C, D. Two similar sections from an older plant. Xy stem apex; shj petlolar sheath. and from the tissue immediately about the stem apex. At its base the sheath of the third leaf is already completely developed and surrounds the young fourth leaf (/*), which in this section was cut horizontally and shows plainly its large apical cell. The stem apex, which lies directly below the younger leaf
. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. Fig. 48. A, B. Two sections of terminal bud of a young sporophyte of Helminthostachys. C, D. Two similar sections from an older plant. Xy stem apex; shj petlolar sheath. and from the tissue immediately about the stem apex. At its base the sheath of the third leaf is already completely developed and surrounds the young fourth leaf (/*), which in this section was cut horizontally and shows plainly its large apical cell. The stem apex, which lies directly below the younger leaf, was cut obliquely in this series and did not show the form of the apical cell plainly, but in a young plant of about the same age (fig. 47, C) the apical cell showed that it was regularly trian- gular in form, seen in cross-section. At the level of the stem apex the second leaf shows a single vascular bundle which may be continued undivided upward, or it may divide into two bundles in the petiole. In regard to the structure of the petiole, therefore, Helminthostachys is to some degree intermediate between Botrychtum. and Ophioglossum. The young trace of the third leaf can be seen at this level as an oval mass of undifferentiated cam- bium. Immediately below the stem apex the cells are smaller than is the case in the young sporophyte of Botrychtum, but one can not make out the beginning of a central procambium cylinder. The smaller cells in the region immediately underlying the stem apex may be explained by the fact that in these young plants there is no pith developed within the axial stele as there is later on. The youngest root in this. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Campbell, Douglas Houghton, 1859-1953. Washington, D. C. , Carnegie Institution of Washington
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