Differentiation of the Spiral Vessels in Ricinus communis

The development of the spiral vessels in Ricinus communis may be observed in the young internodes of the growing shoot. 2. Multinucleate coenocytes differentiate from uninucleate procambial cells. These increase in size in successive internodes and may be observed in macerated material. The coenocytes range in length from 90 to at least 2500 μ, and the maximum number of nuclei observed is twenty-three. 3. As the developing vessel expands, the cell wall does not thicken measurably. When the maximum expansion is reached, a fine spiral of cellulose is laid down throughout the entire length of the vessel. This increases in thickness and begins to lignify when about 2 μ wide (in transverse section). 4. The development of the spiral and the initial lignification is presumably a rapid process, since the intermediate stages of semilignification are relatively rarely observed. Lignification is presumably a periodic process and may occur most actively in the early morning. The lignified spiral continues to thicken, but at this stage cellulose deposition and lignification keep pace with each other. 5. The protoplasm of the developing vessel does not visibly disintegrate during lignification, so that this process is not dependent on any visible breakdown of the protoplasm. This fact raises a question as to the source of the suberin and lignin materials in the endodermis of the root, and also entails a reconsideration of the problem of the entrance of solutes from living cells into allegedly empty spiral elements of the root hair region of the root. 6. Whether the hypertrophy of the nucleus is due to an increase of chromatin material or of nuclear sap, or of both, remains undetermined. 7. The question of polyploidy or of giant chromosomes in the hypertrophied nucleus remains for future solution.