The anthocyanin variegation due to mutable genes gives bud variation in accordance with a definite mechanism of ontogeny. In the variegated azaleas, bud variations occur in various directions, including those to the ground colour. These sports can be explained by recurrent mutation, and sometimes by somatic rearrangement of tissues. The fringed flowers ofRhododendron, Punica, Chaenomeles, andCamellia are regarded as periclinals with mutated, self-coloured meso-histogens. In certain other plants however fringing does not appear in similar periclinals, owing to differences in the extent of development of the ecto-histogen in corolla ontogeny. Sometimes the mutated or the genotypically different mesohistogen does not affect the flower colour or coloration, because the tissues do not contain any pigment.
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