rectiserial

from The Century Dictionary.

• Disposed in a right line; rectilinear or straight, as a row or series of parts.
• In botany, disposed in one or more straight ranks: specifically used by Bravais, in contrast with curviserial (which see), to describe those forms of phyllotaxy in which a second leaf soon stands exactly over any given leaf, and thus all fall into right lines.

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

• adjective (Bot.) Arranged in exactly vertical ranks, as the leaves on stems of many kinds; -- opposed to curviserial.

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

• adjective botany Arranged in exactly vertical ranks, as leaves on stems.