Nature and development of plants . the book. 123. The Sporophylls of Angiosperms.—The flower is oftenconsidered as one of the most characteristic features of theangiosperms, but this structure contains as its essential organsone or more sporophylls and the term flower could be appliedquite as well to the association of these organs in the ferns andgymnosperms. 345 346 SIoROPHYLLS OF ANGIOSPERMS The sporophylls, like all organs of the plant, show a wide rangeof variation and they are generally associated with more or lessmodified leaf-like organs which serve to protect them. Theseleaf-like orga
Nature and development of plants . the book. 123. The Sporophylls of Angiosperms.—The flower is oftenconsidered as one of the most characteristic features of theangiosperms, but this structure contains as its essential organsone or more sporophylls and the term flower could be appliedquite as well to the association of these organs in the ferns andgymnosperms. 345 346 SIoROPHYLLS OF ANGIOSPERMS The sporophylls, like all organs of the plant, show a wide rangeof variation and they are generally associated with more or lessmodified leaf-like organs which serve to protect them. Theseleaf-like organs are known as the floral envelope or perianth anddoubtless arose in many forms through the sterilization and modi-fication of the sporophylls (Fig. 261 A, 1). The microsporo-phvlls, often called stamens, usually consist of a stalk or fila-ment and a four-lobed spore-bearing part, the anther (Fig. 261 A,2). In cross-section, the anther is seen to consist of four spo-rangia in which the microspores originate in tetrads as in the. Fig. Flower and sporophylls of Angiosperms: 1, flower ofSedum with leaf-like perianth, p; mierosporophylls, s; megasporophylls,c. 2, microsporophyll of the buttercup, showing four-lobed anther andfilament. 3, diagram of a cross-section of an anther, showing the break-ing down of the tissue about the four sporangia and the beginning of theopening of the anther. 4, one of the sporangia from a young anther, asseen in cross-section—in, spore mother cells. At the right a mother cellforming four microspores, the upper one being characteristic of mono-cotyledons and the lower of dicotyledons. DEVELOPMENT OF PLANTS 347 preceding groups (Fig. 261A, 3, 4). At maturity, the twosporangia on each side of the anther usually merge into onecavity, owing to the breaking down of the intervening anther opens in a variety of ways, as by slits and pores,permitting the scattering of the spores (Fig. , 3). The
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