Beiträge zur Taxonomie und Chorologie der mitteleuropäischen Utricularia-Arten 2. Androsporogenese,Chromosomenzahlen und Pollenmorphologie

• 1 Microsporogenesis and pollen development in U. vulgaris L., U. intermedia Hayne, and U. minor L. occur typically. In U. australis R. Br., U. ochroleuca Hartm., and U. bremii Heer formation of micronuclei, micropollen, of polyades and abortion of pollen were observed. These aberrations may be responsible for the often affirmed sterility of the mentioned taxa.
• 2 In U. vulgaris L., U. australis R. Br., U. intermedia Hayne, U. ochroleuca Hartm., and U. minor L. the number of chromosomes is n = 22. In U. australis R. Br. and U. ochroleuca Hartm. we occasionally counted n = 18, 19, 20, 23 or 24 chromosomes.
• 3 The pollen grains of all species but U. bremii Heer are 10–19-stephanocolporate. The endoapertures form an endocolpus transversalis; syncolpy of the ectoapertures occurs here and there. The size of normal pollen grains is for the polar axis 25–45 μm, for the equatorial diameter 22–38 μm. The exine is punctitectate; bacules infratectales occur.
• 4 The pollen grains of U. bremii Heer are irregularily spiroaperturate. Their surfaces look like the windings of the brain.
• 5 The pollen grains of the centraleuropean species represent the most derived type of the genus.