. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 638 FILICES. times arise from the surface of the frond, while at other times they spring from below, having a cutieular covering in the form of an indusium or involucre (fig. 882). The clusters of thecas are called sori (fig. 883). The margin of the frond sometimes is folded so as to cover tlie thecse, and at times the whole frond is converted into clusters of thecse. The spores when sown give rise to a prothallus (pro- thallium), which bears anther- idia and archegoni
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 638 FILICES. times arise from the surface of the frond, while at other times they spring from below, having a cutieular covering in the form of an indusium or involucre (fig. 882). The clusters of thecas are called sori (fig. 883). The margin of the frond sometimes is folded so as to cover tlie thecse, and at times the whole frond is converted into clusters of thecse. The spores when sown give rise to a prothallus (pro- thallium), which bears anther- idia and archegonia (p. 280). The antheridia are ia the under surface of the prothallus, and consist of cellular papillse, having a central cavity. This cavity contains free cellules, within each of which there is a ciliated spiral filament or spermatozoid. These cellules are discharged by a rupture at the apex of the antheridium. The spiral filaments then burst the cellules, and being set free reach the cellular body con- taining the embryo-germ, or archegonial cell, embedded in the substance of the prothallus. The archegonia are larger than the antheridia, and present a canal leading to the germ-cell, which canal remains closed till the period when the spermatozoid is matured. After fertilisation the archegonial cell enlarges, develops numerous cellules, and forms the true sporangiferous frond of the fern.—Ferns abound in moist insular climates. They characterise the New Zealand Flora. They are elegant leafy plants, occurring chiefly in moist insular climates, and abounding in the tropical islands. In mUd and warm climates they occur in the form of large Tree-ferns, Fig. 881. Khizome of Scolopendrium vulgare, "with several fronds (leaTes),/',/",/'",/"", in different degrees of development. In /' and /", the eireinate or gyrate vernation is seen. In S"", the linear transverse sori or clusters of thecse are seen, having the appearance of dark lines on th
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
