Abstract
At meiosis in PMCs of the triploid Fritillaria camschatcensis (2n=36), almost all of the three homologues, each in a basic chromosome complement of 12, are formed trivalent associations. Their frequency distribution at first metaphase was found to be from 5III to 12III with the mean number of 10. 28III per cell in a total of 75 complete cells. Among the three distinguishable components of a chromosome complement, which consisting of two M, five S1 and also five S2 types, the frequency of trivalent formation was not recognized to be different statistically.
Based on the situation of kinetochor association, metaphase configurations of trivalent chromosomes are distinguishable as comprising the following three types; viz. IIIK, IIIK' and IIIk types (cf. Matsuura, 1949: to this classification). These types were found to occur in the following frequencies; IIIK in 26.6 per cent, IIIK' in 65.9 per cent and IIIk in 7.5 per cent in a total of 440 trivalents.
Univalent chromosomes found at first metaphase have the mean number of 1.72 per cell, while the mean of univalents lagged in the equatorial plate at first anaphase is 0.61 per cell in a total of 684 cells. It can be statistically confirmed that the frequency of lagging univalents is significantly different between the M chromosome and the S (S1 and S2) chromosome, the M univalents being more frequent than the S ones. Trivalent chromosomes are almost disjoined 1 to 2 at first anaphase. Where the disjunction of 1 to 1 occurs, the remaining 1 chromosome (univalent) an equatorial plate has been observed to be more frequent in the M type than in the S type.
The lagging univalents found at first anaphase are divided at first telophase and each of them formed the micronuclei, their mean number being 1.90 per cell in a total of 119 cells.
