Ecological trends and relations to life forms

Generally, we did not find any ecologically significant features even though the material comes from an extremely wide ecological spectrum. Ring-porosity occurs in all sites analyzed, e.g. Myricaria germanica growing in a river bed in front of a glacier of the Alps, as well as Tamarixgallica growing on dunes around a lake in a hyperarid climate. We observed only one exception: Tamarix articulata growing in a plain around a village in the Central Sahara does not form an earlywood zone and therefore rings are indistinct (Fig. 3).

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Left Fig. 14. Square groups of sclereids are arranged in tangential layers between dilated rays in the phloem. The groups are tangentially separated from unlignified parenchyma cells. Ray cells are primarely un-lignified. Stem of a 1.2 m-high shrub, riverbed, subalpine zone, temperate climate, Morteratsch Glacier forefield, Switzerland. Myricaria germanica, transverse section.

Right Fig. 15. Sickle-shaped groups of sclereids are arranged in tangential layers between rays in the phloem. The groups are tangentially separated of unlignified parenchyma cells. Groups of sclereids in the rays correspond with the tangential layers between them. Stem of a 5 m-high tree, dune, hyperarid climate, Germa, Libya. Tamarix balanse, tangential section.

Left Fig. 16. Similar anatomical structure to that in Fig. 15. Xylem formation is in process (March 07). Stem of a 5 m-high tree, dune, hyperarid climate, Germa, Libya. Tamarix gallica, transverse section.

Right Fig. 17. Phloem structure of the first three rings. The first ring outside the cambium contains parenchyma and sieve tubes. Sieve tubes collapse afterwards and are no longer visible. Stem of a 5 m-high tree, dune, hyperarid climate, Germa, Libya. Tamarix gallica, transverse section.

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