A´trosanguin´eous (ater, black; sanguineus, blood, bloody), dark purple; dark blood color.

Atten´uate (attenuatus, pp. of attenuare, make thin, weaken, lessen, < ad, to, + tenuare, make thin), becoming gradually narrowed or smaller.

Auranti´aceous (aurantium, an orange), orange-colored.

Aur´eous (aureus, of gold, golden, < aurum, gold), golden-yellow; yellow with a slight tinge of red.

Auric´ulate, Aur´iform (auriculatus, < auricula, the external ear), ear-shaped.

Auto-basid´ium (actus, an act, dim. of Gr—a base, + basidium), an unseptated basidium giving rise at the apex to four slender sterigmata (sometimes fewer, sometimes more), each bearing a spore.

Auton´omous (Gr—independent; of one’s own free will; Gr—self, + Gr—hold sway), said of plants that are perfect and complete in themselves; not forming part of a cycle; independent.

Ax´is (axle, axis, pole of the earth), the central line of growth; stipe, stalk, etc.

Azo´nate (Gr—without, + L.zona, a zone), without zones or circular bands of different color.

Ba´dious (badius, bay), bay; reddish-brown; chestnut color.