On the Phyllotaxis of the Ulmus Seedling

1. Goebel’s conception that the distichy of the foliage leaves of the elm tree is due to the abortion of the two upper leaf rows of the dorsiventral shoot, is not supported by the facts. 2. The main axis of the seedling in the investigated specimens was found to be orthotropic and radially symmetrical throughout; all laterals, the pseudoterminal sympodial branches included, are dorsiventral. 3. All foliage leaves are arranged in phyllotactical systems of the main series. 4. In the basal region of the main axis the divergence is about 135°, increasing in some specimens in the higher region even up to 180°. In the regions where the divergence is not increased, binding whorls are formed in a decussate arrangement. 5. In all lateral branches the divergence is about 180°. A fixed spatial relation is established between the dorsiventrality factors and the two leaf rows, ensuring a regular distichy.