Initiation of the Cone Gall of Witch Hazel

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Abstract
A substance that initiates, stimulates, and directs development and differentiation has been found in the cells of the cone gall of witch hazel. It is injected into the young leaf by "stings" of an aphid (Hormaphis hamamelidis) which feeds on the neoplasm induced by its presence. Cells receiving the sting material dedifferentiate, undergo rapid mitosis, and redifferentiate into cells of other and diff. tissues which organize the gall. When injected directly, the material is seen first in the cytoplasm as a single globule containing, usually, 1 refractory crystalloid. The globule enters the nucleus and then the nucleolus, where the crystalloid breaks up. When the injn. is intercellular, the globule is much larger and at first does not show crystalloids. In either case the end result is the entry of crystalloids into the nucleolus where they break up. As mitosis approaches, the bodies become more numerous, and are distributed to the daughter nuclei. They are not capable of self-propagation. For gall formation to continue normally, additional material must be injected repeatedly into the leaf. Only the stem mother can initiate gall formation. Tissues differentiated in the gall do not revert to normal leaf tissues.

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