Summary Details of male meiotic course and pollen fertility have been investigated in 45 species of dicotyledonous plants from the chromosomally unexplored area of the Mandi district, between the altitudinal ranges of 800 to 3360 m. All the species have been worked out cytologically for the first time from the study area. The meiotic chromosome count of n=9 for Impatiens micranthemum is the first ever chromosome report for the species. A new intraspecific 12x cytotype (n=42) has been reported in Potentilla gerardiana, supplementing the earlier reported cytotypes (2x, 8x). A new cytotype has been reported in Gentiana argentea (n=9), supplementing the earlier Indian report of n=10. Out of a total 45 species, 31 species (68.89%) showed normal meiotic course and high pollen fertility (91-100%), while 14 species (31.11%) depicted various meiotic irregularities and some pollen sterility (4-40%). The phenomenon of cytomixis involving inter-pollen mother cells (PMCs) migration of chromatin material has been reported in 3 species, Clematis grata (n=8), Gentiana aprica (n=10) and Lamium album (n=9). In these species, cytomixis induces various meiotic abnormalities (enucleated, hypo-, hyperploid, tripolar and multipolar PMCs, chromatin stickiness, laggards and chromatin bridges at anaphases and telophases and micronuclei) and consequently some pollen sterility and variable sized pollen grains. Besides, non-synchronous disjunctions of bivalents at anaphases, abnormal spindles, and interbivalent connections during diakinesis/metaphase-I, univalents and multivalents have also been reported in certain cases. The chromosome counts in the remainder of the species substantiate previous counts by other researchers. Mandi district, a gateway to Himachal Pradeshʼs most famous places, including Kullu, Manali, and Lahaul-Spiti, lies between 31°13′50″ and 32°04′30″N latitude and between 76°37′20″ and 77°23′15″E longitude and is situated on the left bank of the river Beas in the foot hills of the Shivalik range. The vegetation of hills around Mandi is varied and the geographical location, climate, and topography of the district have contributed to characteristic vegetation and flora. The forests here support and preserve a variety of flora and fauna. The region is primarily dominated by deciduous trees. It is sub-tropical in the valley and tends to be temperate on the hill tops. The vegetation constituting the forests falls under four main categories: (1) Himalayan Sub-Tropical Pine Forests, (2) Himalayan Moist Temperate Forests, (3) Sub-Alpine Forests, and (4) Alpine Forests. Key wordsFor many decades, the Himalayas have attracted a galaxy of researchers from various disciplines on a global scale. So far, studies undertaken pertain either to floristic diversity or ethnobotany (Chowdhary and

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Ageratum belongs to tribe Eupatoriae of family Asteraceae. In the present study floristic forays revealed the prevalence of two species of the genus in North India namely, A. conyzoides and A. houstonianum. Two morphovariants were observed in both the species. The plants were found to differ on the basis of leaf shape and flower colour. Further, analysis of male meiosis revealed the presence of three cytotypes of A. conyzoides and two cytotypes of A. houstonianum. The specimens of A. conyzoides with purple flowers were found to have chromosome count of n=10 (diploid cytotype, 2x) and rarely plants with chromosome count of 2n=30 (triploid cytotype, 3x) were also observed. This is the first report of 3x plants of A. conyzoides from wild. The white flowered plants were found to be tetraploid with n=20. In the specimens of A. houstonianum, the diploid number n=10 was found in white flowered plants while tetraploid number n=20 was found in purple flowered plants. The meiotic course varies from normal to abnormal in some populations of both the species.