Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] A, the archegonium with egg (e) and canal (c); B, antheridium; C, antherozoid, very highly magnified, — Strasburger. forming the neck of the flask. FertiHzation is essentially the same process that has been described for the flowering plants, the sperm cell uniting with the egg cell to form a single cell, the fertilized egg. Sporophyte and Gameto- phyte. — The direct result of fertilization is the growth of the egg cell by repeated
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] A, the archegonium with egg (e) and canal (c); B, antheridium; C, antherozoid, very highly magnified, — Strasburger. forming the neck of the flask. FertiHzation is essentially the same process that has been described for the flowering plants, the sperm cell uniting with the egg cell to form a single cell, the fertilized egg. Sporophyte and Gameto- phyte. — The direct result of fertilization is the growth of the egg cell by repeated divi- sion to form a little fern plant. Later the young plant strikes root, the prothallus dies away, and we have a fern plant which will later in the season pro- duce asexual spores. The leafy fern plant, because it produces asexual spores, is called the sporophyte. The prothallus, which forms the eggs and sperms, both of which are known as gametes, or sex cells, is called the gametophyte. Alternation of Generations. — The fern plant during its entire life thus passes through two entirely different stages, or genera- tions. The spore germinates to form a gametophyte, or sexual generation. This sexual generation in turn produces an asexual generation, or sporophyte. The alternation, in the life history of a plant or animal, of a sexual stage with an asexual stage is called an alternation of generations. General Characters of the Fernlike Plants. —These plants pass through an alternation of generations; they have a distinct root, stem, and leaves; and the stem possesses conducting tubes or Jibro- vascular bundles; these are the distinguishing marks of the ferns and their allies. Fern plants show a great diversity in form and size. They vary from the great tree ferns of the tropics, some of which are thirty to forty feet in height, to tiny forms of almost microscopic size. The leaves of the ferns are among the most complex in form of any that we know. The position and sha
Size: 1324px × 1510px
Photo credit: © Bookworm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
