Bast

Bast, or Phloem, the outer part of the fibrovascular bundle in the higher (vascular) plants, consisting of tough thickened fibres (hard bast) and of sieve-tubes (the vessels of the bast) and cambiform tissue (soft bast). It is formed either directly from the procambial strand of cells, as in the closed bundles of leaves, and of the stems of monocotyledons, ferns, etc. (primary bast), or by the continued activity of the cambium, as in the open bundles of the exogenous stem (secondary bast). With the exception of cotton, all important vegetable textile substances are derived from this tissue, whether in the stem, as in hemp, flax, and linden, or in the leaf, as in Piassaba, Manilla hemp, New Zealand flax, etc. The name is popularly applied mostly to the inner bark of the linden, imported, in mats from Russia. Cuba bast is the product of the malvaceous Paritium elatum.