In this dioecious species known popularly in the west as marijuana and as bhang charas, hashish, ganja in the Orient, the sexuality is highly fragile and susceptible to environmental conditions. In a Russian collection comprising different races and grafts, male meiosis was abnormal in the majority of the anthers (Breslavetz 1935). This led to the formation of tetrads having either two large and two small nuclei or two large or one very large nucleus instead of the usual four nuclei found in the normal plants. In a few, many nuclei were formed in PMC’s. Long before meiotic initiation, abnormalities begin in them and are vivid in early prophase stage (Table 15.1). Sometimes, PMC’s become elongated and divide into two cells even before meiotic initiation. In some, PMC’s grow abnormally in size and have three nuclei, one of them being gigantic in size. All other nuclei undergo abnormal meiosis. Three nuclear plates, incipient spindles, poor chromosome orientation, chromosomes lying away from the incipient spindles, nonbivalency and a large number of univalents (28–30) characterise MI. Anaphasic distribution and subsequent stages are extremely irregular. Pollen grains are empty and variable in size, shape and configuration. These abnormalities are retained by anthers of the male flowers developed after grafting such male plants on female plants. Nearly similar abnormalities in hemp were reported earlier also by Mac Phee (1925) and Hirata (1929). Furthermore, in many monoecious and dioecious hemp varieties, mst flowers are smaller and paler in colour than mft’s.