(1) A haploid plant of T. monococcum was found in a few plants derived from the spikes flowered under the remarkably high temperature caused by the heat radiation from the sun and the earth in early August. (2) The haploid individual was considerably reduced in plant height, size of leaves and spikes, etc. It showed complete sterility under the natural pollination. (3) In first division of PMC-s, 7 univalents were usually observed. Occasionally, two of them conjugated end to end. Chromosome behaviour which may possibly bring about the pollen grain containing the complete set of 7 chromosomes was observed. (4) There are reasons to assume that the appearance of the haploid plant was caused by the extraordinary high temperature acted on the spikes of the mother plant during its flowering time.
In der vorliegenden Arbeit sind die Geschlechtschromosomen von zwei Laubmoosen, nämlich Polytrichum attenuatum und Ceratodonpurpureus untersucht. Ihre Chromosomenfolmeln sind die folgenden. Gametophyt Sporophyt _??_ _??_ Polytrichum attenuatum 6+X, 6+Y 12+X+Y Ceratodon purpureus 12+X, 12+Y 24+X+Y