B. Papp szerk.: Studia Botanica Hungarica 36. 2005 (Budapest, 2005)
Bercu, R.: Contributions to the anatomy of Asplenium ruta-muraria
The transection of the rachis tip (6 cm from the petiole base) shows that the centrally located xylem of the stele has a slightly excavated V-shape, surrounded by phloem, the pericycle and endodermis, the latter with parenchymatous sheath value (Figs 6 A, B) (BERCU 1998e). In the rachis tip two vascular bundles appear, the smaller derived from the rachis stele to form the pinnulae vein (Figs 7A, B). Remarkable is the reduced number of the vascular elements because of the marginal formation of the pinnulae veins. A typical hypodermis is absent (Figs 6A, 7A). The pinnulae appear in cross section to consist of a single layer of irregularly arranged epidermal cells, covered by a thin cuticle (Fig. 8A). On the lower epidermis numerous polycytic and anomocytic stomata occur (VAN COTHEM 1970, DILCHER 1974). The epidermal cells possess wrinkled anticlinal walls (Fig. 8B). The mesophyll is differentiated into palisade tissue (arranged into one row) and spongy tissue. The latter consists of a number of branched and lobed cells arranged into 2-3 rows, forming a system of intercellular spaces (POIRAULT 1893). The poorly developed vascular system of the midrib is represented by a hadrocentric vascular bundle with xylem in a centre position. The bundle is surrounded by a bundle sheath (Fig. 8A). CONCLUSIONS The root of Asplenium ruta-muraria L. has a diarch structure with modified layers of cortex around the stele and a monolayered pericycle. The rhizome (analysed by serial transections) consists of an epidermis, a parenchymatous cortex and a dictyostele, containing a variable number of meristeles. The leaf petiole and rachis exhibit a differential cortex (a sclerenchymatous hypodermis and an inner parenchyma). Close to the rachis tip, the sclerenchymatous hypodermis disappears. Remarkable are the variations in the organisation of the vascular system. The vascular system of the leaf petiole base is monostelic possessing two xylem strings surrounded by phloem elements, while up to the subterminal rachis the monofascicular stele is X-, and than T-shaped. The pinnulae have a heterogeneous mesophyll composed of palisade and spongy tissue, the latter consisting branched and lobed cells. The midrib has a hadrocentric structure. The lower epidermis continuity is broken by a number of stomata of the polycytic and anomocytic type. REFERENCES BERCU, R. (1998Ö): Anatomical modifications of the corm stele in fern Asplenium septentrionale (L.) Hoffm. - Sumarstvo, Journal of Forestry, Belgrade 1: 35-40.
