æcidium

Century Dictionary and Cyclopedia

1. n. A genus of fungi, natural order Uredineæ, now believed to be only a subordinate stage in the development of the genera Uromyces and Puccinia, though this has not been demonstrated in regard to all the reputed species.
2. n. [lowercase] pl. æcidia (ē-sid′ i-ä). The cup-like organ (pseudoperidium) characteristic of the genus or form. See pseudoperidium.

GNU Webster's 1913

1. n. (Bot.) A form of fruit in the cycle of development of the Rusts or Brands, an order of fungi, formerly considered independent plants.