. Botany for high schools and colleges. Botany. 378 BOTANY. Dicksonia growing in the Sandwich Islands constitute the substance known as Pulu, used somewhat in upholstery. Many of the species are now largely grown as ornaments. Ferns first appeared in the Devonian, in which period no less than twelve <reuera belonging to extinct families were represented. In the Carboniferous the genera and species were exceedingly numerous, after which they decreased to the i)resent. Many Tertiary genera extend to the present, and are now represented by living species. Order Marattiacese, the Ringless Ferns
. Botany for high schools and colleges. Botany. 378 BOTANY. Dicksonia growing in the Sandwich Islands constitute the substance known as Pulu, used somewhat in upholstery. Many of the species are now largely grown as ornaments. Ferns first appeared in the Devonian, in which period no less than twelve <reuera belonging to extinct families were represented. In the Carboniferous the genera and species were exceedingly numerous, after which they decreased to the i)resent. Many Tertiary genera extend to the present, and are now represented by living species. Order Marattiacese, the Ringless Ferns. The prothallia of the ringless Ferns are thick, fleshy, and dark green in color. They bear antheridia in depressions upon both surfaces, and in these are pro- duced sperniatozoids bearing much resemblance to those of true Ferns. The archegonia are also deeply sunken in the tissue of the prothallium, and, according to M-Nab, resemble those of the Rhizocarpeae. The asexual generation bears a close resemblance to that of true. Fig. 269. Fig. 268.—A prothallium of BotrycMum Luiiaria, in longitudinal section, ac, an archegonium ; an, an antheridium—near to it are others, one not yet mature, and three empty ones ; w, root-hairs. X 50.—After Hofmeister. Fig. 269.—A longitudinal section of the lower part of a young plant of the same, dug up in September, st, stem ; b, h', h'\ leaves, x 20.—After Hofmeister. Ferns. The plant-body is usually large ; its stem is generally upright, short, thick, and unbranched ; the leaves are circinately developed, as in true Ferns, and are mostly very large, with pinnately or palmately divided laminae ; they are provided with stipules, and in their petioles is found the first collenchyma. The stem develops from a three-sided apical cell, but the root is provided with a group of cells, as in the Phanerogams, The sporangia occur on lateral veins upon the under side of the leaves, and are usually confluent into one body, the sorus (often called
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