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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XII, Part II (1899)

Harper, Robert A.
Nuclear phenomena in certain stages in the development of the smuts,   pp. [475]-Plate IX ff. PDF (8.4 MB)


Page 476


6 Harper-Nuclear Phenomena in the Smuts.
described the so-called copulation of the sporida, in which two
cells become connected by a tube which joins them in pairs very
much as are the conjugating cells of Spirogyra. DeBary' first
pointed out the analogy between this union and the sexual fus-
ions in the Conjugatae, and later2 he presented the evidence
more fully as to whether such fusions are sexual. As favoring
this view he points out: First, the almost invariable occurrence
of the pairing tinder the normal conditions of germination, i. e.,
germination in water. Second, the fusions are usually between
two, and only two, sporidia. In the case of Tilletia, Entyloma,
and Urocystis, when an odd number of sporidia are borne on the
promycelium, the sporidia almost without exception fuse in
pairs, and the odd one is left out and does not fuse with either
of the adjacent pairs, although such a union would be very easy.
This shows that a change has taken place in the fused pairs
which makes a second union difficult or impossible. Most au-
thors since DeBary's earlier paper appeared, have accepted the
view that the sporidial fusions are sexual unions.
  Brefeld3 opposes this view and maintains that such fusing of
cells is mere cell fusion in the sense in which Unger used the
term. According to Brefeld the essential character in a sexual
union of cells lies in the fact, that the conjugating gametes are
incapable of further vegetative growth by division, but become
capable of further development as a result of their union. He
finds that the smut sporidia are capable of unlimited develop-
ment without fusing so long as appropriate nutriment is sup-
plied, and hence concludes that the fusions are purely vegeta-
tive phenomena accompanying, perhaps resulting from, the star-
vation of the sporidia. Such fusions are to be compared to the
unions formed between the germ tubes of various spores or the
hyphae of mycelia, such as will be described more fully below.
  Dangeard4 has more recently studied the nuclear phenomena
  lBeitr. Ser. V, pp. 126-127, and Morph. Phys., und Biol. d. Pilze,
Mycetozoa, u. Bacteria, pp. 181-184.
2 DeBary, Beitr. z. Morph. der Pitze, I, Ser., " Protomyces and
Phy-
soderma. "
3Bot. Untersuchungen Aber Hefenpitze, Hft. V. pp. 33, 49-50,175.
4Dangeard, "Recherches histol. sur la famille des Ustilaginees."
Le
Botaniste, Ser. III., pp. 240, 268; and Le Botaniste, Ser. 4, p. 12.
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476


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