. Nature and development of plants. Botany. Fig. 216. Cross-section of a stem of BotrycMum: p, pith; x, xylem; m, medullary ray; c, cambium; ph, phloem; e, endodermis; cr, cortex.— After Jeffrey. tropics, that the sporangia are developed directly upon the leaves (Fig. 217) instead of upon special branches and that they are sometimes associated together in groups, known as sori ( Fig. 217. Arrangement of the sporangia of an allied order, Marattiales; A, leaflet of Archangiopteris with sporangia on surface of leaf and arranged in groups or sori. B, magnified view of a portion of the leafle
. Nature and development of plants. Botany. Fig. 216. Cross-section of a stem of BotrycMum: p, pith; x, xylem; m, medullary ray; c, cambium; ph, phloem; e, endodermis; cr, cortex.— After Jeffrey. tropics, that the sporangia are developed directly upon the leaves (Fig. 217) instead of upon special branches and that they are sometimes associated together in groups, known as sori ( Fig. 217. Arrangement of the sporangia of an allied order, Marattiales; A, leaflet of Archangiopteris with sporangia on surface of leaf and arranged in groups or sori. B, magnified view of a portion of the leaflet. C, section of leaf, showing two sporangia, the left-hand one in section. sorus) and provided with thickened cells, the annulus—charac- ters that will become conspicuous in the next order. These sporangia originate, however, as in Ophioglossum and open by transverse clefts, which operation is promoted by the unequal drying of the thick- and thin-walled cells of the annulate forms. (a) The Gametophyte.—The gametophyte or sexual genera-. 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 Curtis, Carlton Clarence, 1864-1945. New York, H. Holt
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