. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. 52 THE OPHIOGLOSSALES is in Ophtoglossum and Botrychium lunaria, approaches the circinate form of that of the Marattiaceae and the typical ferns. The young vascular bundle is now clearly evident, lying somewhat toward the inner side of the leaf, and it can be readily followed downward until it joins the root bundle, with which it is continuous. In B. virginianum, while the cotyledon is still quite small, the second leaf appears close to the stem apex and nearly opposite the
. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. 52 THE OPHIOGLOSSALES is in Ophtoglossum and Botrychium lunaria, approaches the circinate form of that of the Marattiaceae and the typical ferns. The young vascular bundle is now clearly evident, lying somewhat toward the inner side of the leaf, and it can be readily followed downward until it joins the root bundle, with which it is continuous. In B. virginianum, while the cotyledon is still quite small, the second leaf appears close to the stem apex and nearly opposite the cotyledon, the sheathing base of which surrounds the stem apex, together with the young second leaf. The growth of the second leaf is also probably from a tetrahedral apical cell, and this is the case with all of the later leaves. While the second leaf is still very small, there begins the differentiation of the corresponding leaf trace, which joins the bundle of the primary root close to the point at which it gives off another bundle destined for the second root, the apical cell of which is cut out from the tissue near the base of the second leaf, at a point almost directly opposite the cotyledon. Indeed, the second root may be said to bear much the same relation to the second leaf that the primary root does to the cotyledon (fig. 35, jB).. Fig. 36.—Botrychium lunaria (after Bruchmann). A, B. Young embryos. X225. C, D. Older embryos. The cotyledon and stem apei, st, are developed much later than in B. virginianum. The cotyledon in B. virginianum (Hg. 7) is extraordinarily developed, reaching a size that probably is unequaled by any other fern. Its slender petiole reaches a length of 5 to 6 centimeters, and the lamina, unlike the simple oval primary leaf of Ophioglossum, is ternately divided and the segments deeply cut. The venation, instead of being reticulate as in Ophioglossum, is apparently pinnate, but this is really the result of an unequal dichotomy, as it is in the ul
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