amphigen

from The Century Dictionary.

• noun In botany, a thallogen: a name applied by Brongniart to those cryptogams (the algæ, fungi, and lichens) which increase by development of cellular tissue in all directions, and not at the summit of a distinct axis.
• noun 2. In chem., an element, like oxygen, capable of forming with other elements acid and basic compounds.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.), rare An element that in combination produces amphid salt; -- applied by Berzelius to oxygen, sulphur, selenium, and tellurium.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry, obsolete An element that in combination produces amphid salt; applied by Jöns Jacob Berzelius to oxygen, sulphur, selenium, and tellurium.