What is "libriform"

Libriform \Li"bri*form\ (l[imac]"br[i^]*f[^o]rm), a. [Liber + -form.] (Bot.) Having the form of liber, or resembling liber.

Libriform cells, peculiar wood cells which are very slender and relatively thick-walled, and occasionally are furnished with bordered pits.
--Goodale.

a. (context botany English) Resembling or having the form of liber, or bast.