Studies in the Capparidaceae

III. The prochromosomes of Polanisia trachysperma Torr. & Gray and Gynandropsis pentaphylla DC

Abstract

The prochromosome and chromosome cycle has been traced in the somatic divisions of Polanisia traclzyspermna (2n=20). Prochromosomes are derived directly from the telophase chromosomes by the persistence of the chromatic material in the attachment constriction region.
Fibres are not apparent in the resting nuclei of Polanisia, while they are comparatively prominent in the telophases.
Earlier stages of meiosis in Gynandropsis pentaphylla (n=17) are described.
The fall diploid number of prochromosomes (34) is present in the telophase of the last premeiotic division, as also in the resting stage of the nucleus of the pollen mother cell, and the theory of the pairing of the prochromosomes in the premeiotic nucleus is not accepted. Chromonemata are reported in the chromosomes and evidence is submitted which suggests that the chromosome structure as well as the chromosome cycle in plants with prochromosomes are in essence the same as in plants without prochromosomes in both somatic and meiotic divisions.
The nucleolus is organized in Polanisia by a pair of satellited chromosomes.
A portion of the chromatin contained in the chromosomes is found to be accumulated an the surface of this primary nucleolus, whose surface consequently presents darkly stained patches from late telophase up to Tate prophase.
The close association of the prochromosomes with the nucleolus at telophase and early prophase is explained an this basis.
In conclusion, I have great pleasure in recording my gratitude to Professor R. Ruggles Gates, for suggesting this piece of work in connection with my work an the Capparidaceae and for helpful criticism and guidance.