Enation

In field infections, the enations are very small and appear as gray streaks on the backs of the leaves. However, conspicuous enations appear on plants inoculated and reared in the glasshouse (Lindsten, 1961a; Catherall, 1970).

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Irrespective of how the terminal position of sporangia on short lateral branches evolved, we should keep in mind that it was an important step in positioning the developing sporangia so that they could be protected by enations and microphylls.

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Infected trees are stunted, with narrow leaves, often with large enations on their underside.

Source: wiktionary

Enation is characterized by the formation of very small, leaflike outgrowths — enations — from the lower surface of leaves, usually along the larger veins (fig. 116).

Source: wiktionary