Discussion in relation to previous studies

The xylem of all genera analyzed here (shrubs and dwarf shrubs), except for Chrysothamnus, have been characterized before. Gregory (1994) mentioned 105 references on 25 genera. The xylem of dwarf shrubs (Rhamnus) has been described only by Schweingruber (1990) and Akkemik et al. (2007). Holdheide (1951) described the bark of Frangula alnus and Rhamnus cathartica in detail. The bark of 16 species is described here for the first time. As previous authors realized, the family is anatomically divided into three groups. Paliurus and Ziziphus are diffuse-porous and have a few large, solitary vessels, whereas Frangula is semi-ring-porous with uniformly distributed vessels. Vessels of all other genera are diagonal or even dendritically arranged. Within the genus of Rhamnus, some species can be differentiated by ray width. Anatomical differences between life forms (shrubs and dwarf shrubs) from different vegetation belts, e.g. hill zone versus alpine zone, seem to be absent.

Present features in relation to the number of analyzed species

IAWA code frequency

Present features in relation to the number of analyzed species

IAWA code frequency

Total number of species



growth rings distinct and recognizable









vessels in intra-annual tangential rows



vessels in diagonal and/or radial patterns



vessels in dendritic patterns



vessels predominantly solitary



vessels in radial multiples of 2-4 common



vessels in radial multiples of 4 or more common



vessels predominantly in clusters



vessels with simple perforation plates



intervessel pits alternate



helical thickenings present


108 110 136 144 R1 R2 R3 R4 R6 R6.1

4 20

3 13 16 17

ray: heterocellular with 2-4 upright cell rows (radial section) 2

39.1 vessel cell-wall thickness >2 pm

40.2 earlywood vessels: tangential diameter 20-50 pm

41 earlywood vessels: tangential diameter 50-100 pm

42 earlywood vessels: tangential diameter 100-200 pm 50 <100 vessels per mm2 in earlywood

50.1 100-200 vessels per mm2 in earlywood

50.2 200-1000 vessels per mm2 in earlywood 56 tylosis with thin walls common 58 dark staining substances in vessels and/or fibers

60 vascular/vasicentric tracheids, Daphne type

61 fiber pits small (<3 pm = libriform fibers)

68 fibers thin-walled

69 fibers thick-walled

70 fibers thin- to thick-walled 70.2 tension wood present

75 parenchyma absent or unrecognizable

76 parenchyma apotracheal, diffuse and in aggregates 79 parenchyma paratracheal 89 parenchyma marginal

96 rays uniseriate

97 ray width predominantly 1-3 cells

98 rays commonly 4-10-seriate 100.2 rays not visible in polarized light 103 rays of two distinct sizes (tangential section)

ray: all cells procumbent (radial section) ray: all cells upright or square ray: heterocellular with 1 upright cell row (radial section)

ray: heterocellular with >4 upright cell rows (radial section) rays with sheet cells (tangential section) prismatic crystals present druses present groups of sieve tubes present groups of sieve tubes in tangential rows distinct ray dilatations sclereids in phloem and cortex sclereids in radial rows sclereids in tangential rows R6.2 sclereids in tangential arranged groups, Rhamnus type R7 with prismatic crystals R8 with crystal druses

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