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Seedling trees were grown in complete nutrient solution and in one without added boron for a period of 5 years. Roots and shoots of boron‐deficient plants showed a variety of symptoms which were involved in the disruption of normal cellular differentiation. Abnormalities in structure, cell shape, wall conformation and rigidity are described for both primary and secondary tissues. The persistence of the trees in spite of the death of apical meristems and local or seasonal variations are discussed.

The development of buds and their vascular connections are described for Helianthus annuus and H. bolanderi. Bud meristems of H. annuus usually become isolated by parenchymatization of the bud traces in the cortical zone. If the buds are induced to grow as a result of decapitation of the terminal meristem, a continuous range between typical primary connections and pseudo‐adventitious connections are made between the main axis and the lateral buds. Considerable growth of the branches occurs within 48 hours after decapitation. Axillary buds of H. bolanderi grow continuously, and both the meristem and vascular system of the buds are derived directly from the apical meristem of the shoots.

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