. Fossil plants : for students of botany and geology . Paleobotany. LIl] GNETTTM 463 archegonia: in some species the megaspore contains numerous free nuclei all of which are potentially sexual; after fertilisation a sterile nutritive tissue, or endosperm, is formed in the lower part of the spore. In Gnetum Gnemon the endosperm is often formed before fertihsation. In the great reduction of the female apparatus and in the nature of the endosperm Gnetum^ agrees much more closely with Welwitschia than with Ephedra. Attention has been called to certain resemblances between the seed of Gnetum and. F
. Fossil plants : for students of botany and geology . Paleobotany. LIl] GNETTTM 463 archegonia: in some species the megaspore contains numerous free nuclei all of which are potentially sexual; after fertilisation a sterile nutritive tissue, or endosperm, is formed in the lower part of the spore. In Gnetum Gnemon the endosperm is often formed before fertihsation. In the great reduction of the female apparatus and in the nature of the endosperm Gnetum^ agrees much more closely with Welwitschia than with Ephedra. Attention has been called to certain resemblances between the seed of Gnetum and. Fia. 817. Seed of Gnetum africanum. a, outermost envelope; v, vascular strands; 5, outer integument; /, flange of micropylar tube; n, nueellar cap; c, inner integument; p, endosperm. (After Mrs Thoday.) that of Bennettites^. For convenience of comparison a diagram- matic section of a seed of Gnetum africanum is reproduced in fig. 817. The outermost envelope, a, forms a green succulent covering free to the apex; the middle envelope, h (outer integument), is free from the other envelopes except at the apex where it is locked to the inner integument by the downward growth of a flange,/, from the apical region of the inner integument; the inner 1 Pearson (09); see also Karsten (92); (93^); Lotsy (99). 2 Berridge (11); (12); Thoday (Sykes) (11).. 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 Seward, A. C. (Albert Charles), 1863-1941. Cambridge : University Press
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishercambr, bookyear1898
