. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. 106 THE OPHIOGLOSSALES unequal dichotomy, like that which results in the first divisions of the primary leaves. In large plants the leaves may reach a length of 30 or 40 centimeters. The petiole is nearly cylindrical at its base, but higher up becomes slightly winged at the margins, these wings passing into the lamina. A section of the petiole taken a little way below the insertion of the sterile lamina shows that the peduncle of the sporangio- phore is recognizable for a lo
. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. 106 THE OPHIOGLOSSALES unequal dichotomy, like that which results in the first divisions of the primary leaves. In large plants the leaves may reach a length of 30 or 40 centimeters. The petiole is nearly cylindrical at its base, but higher up becomes slightly winged at the margins, these wings passing into the lamina. A section of the petiole taken a little way below the insertion of the sterile lamina shows that the peduncle of the sporangio- phore is recognizable for a long distance below the point at which it becomes free, its adaxial surface projecting as a rounded ridge between the wings on the margin of the petiole (fig. 78, D). In texture the leaves are firmer and more leathery than in any of the other Ophioglossaceae, and in this respect, as well as in their venation, they closely resemble such Marattiaceae as Dancea and Angiopteris. The sporangiophore is to some extent intermediate in character between that of Ophioglossum and Botrychium. It is inserted near the junction of the lamina and petiole, but, as already stated, can be traced for some distance below the point where it joins the petiole. The fertile portion of the sporangiophore, which may reach a length of nearly 10 centimeters, is composed of crowded, short branches, upon. Fig. 79. A. Rhizome of He/min/AoJ/acA^j. 5/1, stipular sheath. B. Section of rhizome. The dark spots are tannin sacs. C. Tannin sacs from the rhizome. which are borne groups of nearly globular sporangia much like those oi Botrychium. The ends of the branches which bear the sporangia may be expanded into small leaf- like organs which, under exceptional conditions, look much like small leaves, upon which the individual sporangia are borne (see Bower 9, fig. 239). The stem in Helminthostachys almost always remains unbranched, except that there may be formed adventitious buds somewhat as in Botrychium. The
Size: 1946px × 1285px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
