Spurious Secondary Association and Asymmetric Spindles in a Luzula

抄録

1. In aceto-carmine smears of Luzula campestris, the six bivalents at metaphase I appear to be associated in groups rather than spread out at random. The two most common arrangements are three groups of two bivalents and a one-two-three arrangement.
2. In sectioned material, no such grouping is present. The secondary associations of the smears are therefore artifacts.
3. In the sectioned material, the pollen-mother cells and the spindles at the equatorial plate are frequently asymmetric. The chromosomes vary in arrangement on the plate, to a large degree in accord with the asymmetry of the spindle. The three types of chromosome arrangement are the circular, the triangular, and the type with two rows.
4. Comparisons, some of them quantitative, can be made between the arrangements of chromosomes in the sections and those of the smears. Factors which may aid in the production of the spurious secondary association are discussed.
The writer is indebted to Dr. G. LEDYARD STEBBINS, Jr. for suggesting a cytological study of L. campestris, and to him and to Dr. ALOHA HANNAH for pertinent suggestions during the course of this work.