Characteristics of the phloem and the cortex

Thin-walled, unlignified sieve tubes and parenchyma are annually layered (Fig. 83), but these cell types cannot be distinguished. Sclerenchyma cells form an arc outside an annual layer (Fig. 84), and are laterally present in groups (Figs. 85 and 86) or are missing (Fig. 83). Ray dilatations are distinct (Figs. 84 and 85). A phellem is present in all species. In most cases it forms annual layers consisting of large square, thin-walled cork cells and thicker-walled small phloem cells (Fig. 87). Rhyti-dioms (dead phloem and phellem) do not last long on the bark (Fig. 88).

large v small v primary r secondary r

Characteristics Liana Tree

Fig. 69. Ring-porous wood with distinct annual rings with many primary and a few secondary rays. Ray width increases with increasing stem diameter. A few secondary rays are initiated. Stem of a climber (liana), on a wall, Mediterranean zone, Samos, Greece. Clematis viticella, transverse section.

Fig. 68. Ring-porous wood with distinct annual rings. Stem of a climber (liana), hedge, hill zone, Trentino, Italy. Clematis vitalba, transverse section.

Fig. 69. Ring-porous wood with distinct annual rings with many primary and a few secondary rays. Ray width increases with increasing stem diameter. A few secondary rays are initiated. Stem of a climber (liana), on a wall, Mediterranean zone, Samos, Greece. Clematis viticella, transverse section.

Fig. 70. Semi-ring-porous wood with distinct annual rings. Ray width and vessel fiber zones increase with increasing stem diameter. Ray cells are unlignified (blue). Stem of a climber (liana), spruce forest, subalpine zone, Grisons, Switzerland. Clematis alpina ssp. alpina, transverse section.

Left Fig. 71. Semi-ring-porous wood with distinct annual rings. Ray cells are unligni-fied. Stem of an 80 cm-high chamaphyte, Ostrya forest, hill zone, Ticino, Switzerland.

Clematis recta, transverse section.

Right Fig. 72. Semi-ring-porous wood with distinct annual rings. Ray width increases slightly with increasing stem diameter. Ray cells are unlignified. Stem of a chamephyte, Pinusponderosa forest, mountain zone, Colorado, USA. Clematis hirsut-issima, transverse section.

primary ray secondary ray rhytidiome rhytidiome

ph xy ph xy primary ray secondary ray

Characteristics Annual Rings

Left Fig. 73. Semi-ring-porous wood with distinct annual rings, ray width increases with increasing stem diameter. Ray cells are unlignified. Stem of a climber, dry meadow, mountain zone, Colorado, USA. Clematis columbiana, transverse section.

Right Fig. 74. Ring-porous wood with distinct annual rings. With increasing diameter more and more secondary rays are initiated. Stem of a climber (liana), hedge, Mediterranean zone, Provence, France. Clematisflammula, transverse section.

ivp he ivp

Left Fig. 75. Large intervessel pits with horizontally enlarged apertures. Stem of a climber (liana), Ostrya forest, hill zone, Ticino, Switzerland. Clematis recta, radial section.

Right Fig. 76. Helical thickenings in vessels and vasicentric tracheids. Stem of a climber (liana), hedge, hill zone, Trentino, Italy. Clematis vitalba, radial section.

'bpit

'bpit shc

fT ST

Left Fig. 77. Fibers with large bordered pits. Stem of a climber (liana), spruce forest, subalpine zone, Grisons, Switzerland.

Clematis alpina ssp. alpina, tangential section.

Right Fig. 78. Parenchyma is paratracheal, pervasive and marginal. Fibers and vessels are thin-walled. Stem of a climber (liana), spruce forest, subalpine zone, Grisons, Switzerland. Clematis alpina ssp. alpina, transverse section.

Left Fig. 79. Parenchyma arranged paratra-cheal and pervasive. Fibers and vessels are fairly thick-walled. Stem of a climber (liana), hedge, Mediterranean zone, Provence, France. Clematis flammula, transverse section.

Right Fig. 80. Large ray with sheet cells. Ray cell walls are lignified. Stem of a climber (liana), hedge, arid zone, Valle della Luna, Argentina. Clematis montevidensis, tangential section.

Left Fig. 81. Large ray with sheet cells. Ray cell walls are unlignified. Stem of a climber (liana), hedge, Mediterranean zone, Provence, France. Clematis flammula, tangential section.

Right Fig. 82. Large ray with vertically elongated cells. Ray cell walls are thin-walled and unlignified. Stem of a chame-phyte, Pinus ponderosa forest, mountain zone, Colorado, USA. Clematis hirsutis-sima, tangential section.

dead phloem

CU u

u c c dead phloem

cork

Left Fig. 83. Phloem with annual small rectangular sieve tube and round parenchyma layers. Sieve tubes collapse after the second year (dark blue tangential zones). Stem of a climber (liana), spruce forest, subalpine zone, Grisons, Switzerland. Clematis alpina ssp. alpina, transverse section.

Right Fig. 84. The living phloem consists h of small sieve tubes, larger parenchyma cells and an arc of thick-walled sclerenchyma cells (red). The phellogen produces cork cells (unstained rectangular cells outside the blue zone) after one year and was active after approximately 5 years. Stem of a climber (liana), hedge, hill zone, Trentino, Italy. Clematis vitalba, transverse section.

Left Fig. 85. The phloem consist of small sieve tubes, larger parenchyma cells and few sc groups sclerenchyma cells adjacent to the ray. Stem of a climber (liana), hedge, Mediterranean zone, Provence, France. Clematis flammula, transverse section.

Right Fig. 86. The living phloem consists of small sieve tubes, larger parenchyma cells and a few small groups of sclerenchyma cells. The phellogen becomes active after approximately 5 years. Stem of a chame-phyte, Pinus ponderosa forest, mountain zone, Colorado, USA. Clematis hirsutis-sima, transverse section.

Left Fig. 87. Two phellem (cork) layers outside the phloem. The phellem consist of two rows of large, thin-walled cork cells and several rows of fairly thick-walled dead _ phloem cells. Stem of a climber (liana), o spruce forest, subalpine zone, Grisons, Switzerland. Clematis alpina ssp. alpina, transverse section.

Right Fig. 88. Rhytidiome (cork and dead phloem) outside the phellogen with nuclei in the cells. The phellem consist of two rows of large, thin-walled cork cells. Outside the collapsed sieve tubes (dark line) are dead round parenchyma cells and a band of scle-renchyma cells. Stem of a climber (liana), hedge, hill zone, Trentino, Italy. Clematis vitalba, radial section.

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