The Origin and Development of the Apothecium in Collema Pulposum (Bernh.) Ach

The Origin and Development of the Apothecium in Collema Pulposum (Bernh.) Ach

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 edition. Excerpt: ...of the spindle there is a very clearly defined polar aster, the rays of which may be traced far out into the cytoplasm. The nucleole sometimes persists and stains quite deeply after the spindle is fully formed. In late prophases (Figs. 74, 75) the chromosomes are scattered about on the spindle. They are small ovoid bodies about twice as long as wide. Later in the metaphase stage they are aggregated in the center of the spindle. What I take to be an early metaphase shows about twelve chromosomes, which are now split longitudinally (Fig. 73). The first nuclear division in the ascus is preceded by a distinct synapsis stage (Fig. 71) which harmonizes with the conclusions of other writers that this is a heterotypic division separating whole chromosomes. We should expect therefore to find the reduced number of chromosomes in the equatorial plate. Whether my conclusions as to the number in the metaphase stage (twelve) is exactly correct or not, it is at least evident that about twice as many chromosomes appear in the first division in the ascus as in the nuclear divisions in the vegetative hyphae. If a single nuclear fusion has occurred in the life history of the fungus, the reduced number should be the same as that found in the vegetative divisions, which is probably six. Since the number appearing in the first division in the ascus is twelve it follows that there have probably been two nuclear fusions, one certainly in the ascus, the other very probably in the ascogone. I have no preparations showing the spindle of the second division. In the third division there are probably six chromosomes. In Figure 76, which shows this division, there are at least five chromosomes. The figure suggests six, but this is not so evident when studying more

Product details

  • Paperback | 30 pages
  • 189 x 246 x 2mm | 73g
  • United States
  • English
  • black & white illustrations
  • 1236923537
  • 9781236923530