<P> In some eudicot families (Apocynaceae, Convolvulaceae, Cucurbitaceae, Solanaceae, Myrtaceae, Asteraceae, Thymelaeaceae), phloem also develops on the inner side of the vascular cambium; in this case, a distinction between external phloem and internal phloem or intraxylary phloem is made . Internal phloem is mostly primary, and begins differentiation later than the external phloem and protoxylem, though it is not without exceptions . In some other families (Amaranthaceae, Nyctaginaceae, Salvadoraceae), the cambium also periodically forms inward strands or layers of phloem, embedded in the xylem: Such phloem strands are called included phloem or interxylary phloem . </P> <P> Phloem of pine trees has been used in Finland as a substitute food in times of famine and even in good years in the northeast . Supplies of phloem from previous years helped stave off starvation in the great famine of the 1860s . Phloem is dried and milled to flour (pettu in Finnish) and mixed with rye to form a hard dark bread, bark bread . The least appreciated was silkko, a bread made only from buttermilk and pettu without any real rye or cereal flour . Recently, pettu has again become available as a curiosity, and some have made claims of health benefits . However, its food energy content is low relative to rye or other cereals . </P> <P> Phloem from silver birch has been also used to make flour in the past . </P>

Phloem is made up of living cells. phloem takes sugars in the