A Students' Text-Book of Botany Volume 1

A Students' Text-Book of Botany Volume 1

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 edition. Excerpt: ...unicellular and undifferentiated: thus, when the gametophyte is unicellular (e.g. Desmidiese, Diatomacese) the cell itself constitutes the gametangium; and in some multicellular or coenocytic forms (e.g. Zygnemese, Hydrodictyon, Confervoidese) the gametangia are simply ordinary vegetative cells or ccenocytes. In some isogamous Algse, however, the gametangia are differentiated as lateral appendages, and are multicellular, as in the Phseosporese; in Cutleria it is even possible to distinguish the male from the female gametangium. When the gametangium is unicellular or coenocytic, it usually gives rise to a number of gametes; but in the Conjugata; a single gamete is formed. When the gametangium is multicellular, each cell usually erives rise to a single gamete; but in the male gametangium of Cutleria 2-8 gametes are developed in each cell. The female organ, the oogonium, is in all cases unicellular or a cosnocyte; in Sphseroplea it is undifferentiated, retaining the form of a vegetative segment of the incompletely septate plant; in most cases it is more or less spherical in form, and in some species of Coleochsete it is prolonged at the apex into a delicate tube, the trichogyne. It opens, in most cases, by the absorption of the wall, at a point opposite the receptive spot of the oosphere when that is present; but in others (e.g. Volvox, Chara) it remains closed. In the former case the spermatozoid enters by the aperture; in the latter, it bores its way through the wall of the oogonium which becomes mucilaginous at its exposed surface. The oogonium of the Fucaeese, Dictyotacese, and Tilopteridacese, ruptures and sets free the contained female cell or cells. Usually a single female cell (oosphere) is formed in an oogonium, by the rejuvenescence of its...show more

Product details

  • Paperback | 164 pages
  • 189 x 246 x 9mm | 304g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236575245
  • 9781236575241