The Nature of Chromosomes. I. Effects of Reagents on Root Tip Sections of Vicia faba

Abstract

1. Sections of Vicia faba root tips were treated with solutions of tribasic sodium phosphate, acid sodium phosphate, sodium phosphate at pH 5, sodium hydroxide, and pepsin hydrochloric acid respectively. 2. Tribasic sodium phosphate and sodium hydroxide each caused a swelling of the nucleus and chromosomes, and almost eliminated their staining capacity. The effect of the former reagent is the greater. It is considered that the chromatin is dissolved and removed. 3. The nucleolus is shown to consist of two elements, a peripheral and central, the former probably contributing to the formation of the chromosomes. 4. A theory is proposed to account for chromonemata as indicating the presence of a thread of ultramicroscopic genes whose split halves mutually repel each other within the chromosome. 5. The suggestion is made that the visible parts of the chromosome and nucleus form an internal environment for the interaction of the genes, but are not themselves the physical basis of Mendelian heredity. 6. Changes in the constitution of this visible matter might produce a profound effect that only unspecialized forms could survive, gene mutations being responsible for minor changes involving specialization.