adjective.
Arranged in two vertical rows on opposite sides of an axis.
The Century Dictionary and Cyclopedia
Disposed in two rows; biserial; bifarious; dichotomous; specifically, in botany, arranged alternately in two vertical ranks upon opposite sides of the axis, as the leaves of grasses, elms, etc. Also distich.
adjective.
Arranged in two rows on each side of an axis
Word Usage
"In the yew (_Taxus_) the leaves at the ends of the shoots not unfrequently lose their usual distichous arrangement and become arranged in a close spiral manner, the elongation of the shoot being arrested."