1. A review of the literature indicates that two chromosome numbers have been given for Vitis vinifera: n=19 and n=20.
2. The somatic chromosome number of 86 cultivated varieties has been found to be 38.
3. Of 129 seedlings grown from self-pollinated seed of many diploid varieties, all had the normal number 38, except one that was triploid.
4. The chromosome number of Vitis vinifera is n=19, 2n=38. Rarely may clones be propagated that have a hyperploid number. A theory is presented to account for their origin from normal diploids.
5. Seedlessness and coulure, as manifested in some varieties, cannot be attributed to a heteroploid chromosome constitution.
6. The origin of triploid and tetraploid derivatives is described.
7. Intraspecific variation has occurred mostly by the accumulation of genic difierences, without gross alteration in chromosome number or structure.