Meiosis in Pollen Mother Cells of Linum usitatissimum

[摘要] 1. The resting nucleus of the pollen mother cell of Linum usitatissimum contains prochromosomes distributed irregularly throughout the nuclear cavity, but always connected with the reticulum (Fig. 1). 2. With the beginning of the nuclear division occurs the contraction of the nuclear contents away from the nuclear membrane, and at the same time takes place the conjugation of the prochromosomes in pairs (Fig. 2). 3. In the synapsis stage it is observed that the spireme is connected with the nucleolus at one point, its pole ( Fig. 3). Perhaps the contraction of the nuclear contents which occurs in the synapsis stage is due to a concentration of the spireme toward the pole of the nucleolus. During the synapsis stage, the nucleolus produces generally one, rarely two or more, secondary nucleoli (Fig. 3). These sccondary nucleoli connect with the nucleolus at its pole. 4. At the late pachytene stage the spireme seems gradually to lose its chromatin, until all the spireme becomes nearly colourless and enters the achromatene stage (Fig. 5). 5. After the achromatene stage, pairing chromatin appears on the spireme which is connected with the nucleolus (Fig. 6). Perhaps during this stage a movement of chromatin may occur from the nucleolus to the connecting spireme. 6. At the beginning of the first telophase occurs a movement of chromatin from the chromosomes along the fine threads, which connect them with each other, to form irregular masses of chromatin (Fig. 10), and finally all the chromatin concentrates in one place to produce a new nucleolus (Fjg. 11). During this stage, some of the chromosomes disappear, completely losing their chromatin, while others remain as small granules in the nucleolus retaining part of their chromatin (Fig. 11). 7. During the second prophase, the small granules of chromatin seem to reform the chromosomes, gradually receiving chromatin from the nucleolus (Figs. 12 an 13). In the second telophase the same phenomenon as in the first telophase occurs that the chromatin of the chromosomes concentrates in one place to form the new nucleolus (Figs. 14 and 15). These facts indicate that the nucleolus contains the material of the chromosomes. 8. The haploid number of the chromosomes in Linum usitatissimum is fifteen.

[学科分类] 农业科学（综合）