Characteristic features of taxa
Tangentially arranged rectangular groups of sclerenchyma (Figs. 26 and 27) and the presence of mucilage and crystal druses and/ or prismatic crystals and mucilage are characteristic of well-grown individuals. Mucilage is produced in parenchymatic ray cells (Fig. 28) or in ducts within rays (Fig. 29). All of these features are absent in Cristaria dissecta.
Characteristic of the family are many species with large vessels and tangential parenchymatic bands in the xylem. Species with indistinct large rings are common. Bark structures of different species within the family are very similar. Characteristic are the tangential bands of sclerenchyma and the mucilage producing parenchyma cells.
Left Fig. 26. Phloem with distinct ray dilatations and many tangential layers of scler-enchyma located in a bi-annual plant. Root collar of a 40 cm-high hemicryptophyte, abandoned field, submediterranean, Le Puy en Velais, France. Malva moschata, transverse section, polarized light.
Right Fig. 27. Phloem with distinct ray dilatations and many tangential layers of sclerenchyma located in a bi-annual plant. Root collar of a 40 cm-high hemicrypto-phyte, ruderal site, submediterranean, Pos-toina, Slovenia. Malva neglecta, transverse section.
Left Fig. 28. Phloem with distinct ray dilatations and many tangential layers of sclerenchyma. Dilated rings are filled with mucilage (blue). The phellem consists of rectangular, regularly radial oriented cells. Stem of a 1.5 m-high shrub, rock field, thermophile zone, subtropical zone, Buena Vista, Tenerife, Canary Islands. Lavatera acerifolia, transverse section.
Right Fig. 29. Mucilage ducts in large rays. Stem of a 2 m-high shrub, ruderal site, subtropical climate, Tenerife, Canary Islands.
Gossypium herbaceum, transverse section.
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