Five plants produced in a H. lechleri x H. vulgare cross comprised fou
r trihaploids of H. lechleri with 2n = 21 and one aneuploid interspeci
fic hybrid with 2n = 25 26. Somatic cells of the hybrid lacked H. vulg
are chromosomes nos 1 and 6 and one, or two H. lechleri chromosomes, b
ut had two representatives of H. vulgare chromosome no- 7. Chromosome
numbers of meiotic metaphases ranged from 4 to 54 with peaks at or jus
t below euploid numbers corresponding to the prevalent aneuploid chrom
osome number of the hybrid. The cause of chromosome numbers at and aro
und 2n = 14 and 2n = 7 is proposed to be intraspecific, intergenomic e
limination of one and two H. lechleri genomes, respectively, in additi
on to the elimination of all H. vulgare chromosomes. It is suggested t
hat intraspecific, intergenomic elimination occurs in allopolyploids i
n nature, thereby causing reduction in chromosome number within specie
s. Numbers above 2n = 29 are ascribed to spontaneous chromosome doubli
ng- Meiotic irregularities such as misdivisions, ''budding'', telocent
rics, fragmentation of the whole chromosome set, and non-synchronized
divisions were common. The production of ''buds'', generally with few
chromosomes, may have added to the variability in chromosome numbers.