B. Papp szerk.: Studia Botanica Hungarica 36. 2005 (Budapest, 2005)

Bercu, R.: Contributions to the anatomy of Asplenium ruta-muraria

MATERIAL AND METHODS Cross sections of the root, rhizome and leaf were made with a rotary microtome. The samples were stained with alum-carmine and iodine green, and were embedded in Canada balsam. The observations were made with a BIOROM-T bright field microscope, equipped with a TOPICA-1006A video camera. The microphotographs were obtained from the video camera through a computer. RESULTS AND DISCUSSIONS Cross sections of the adventitious root revealed that the cortex is composed of 3^4- layers of large parenchyma cells. The inner layers of cortex cells are modified and have thick walls. KROEMER ( 1903) suggested that this wall thickening was the result of cutinised blade superpositions. Noticed by early authors, the presence of such "curious cells" around the stele has led to the recognition of this tissue belonging to the stele and naming it "sclerenchy

matous mass" (RUSSOW 1872, BlERHORST 1971)ora"stereomicsheath"(DEBARY 1877, OGURA 1938, BERCU 1998a, BERCU et al. 2000) (Figs I A, B). This configuration has led SCHNEIDER (1996) to include this type of root to that of Asplenium. The stele consists of xylem and phloem and is surrounded by the pericycle. The xylem elements are joined together towards the centre by their metaxylem vessels (two for each bundle). The protoxylem vessels (four for each bundle) are in an exarch position and face the pericycle. The phloem sieve cells lacking companion cells are located on either side of the xylem string (Fig. IB). This attributes to the adventitious root a diarch structure. Fig. 1. Cross section of the adventitious root. - A: General view of the root (x269). -B: Detail of the stele (x330): C = cortex, Mx = metaxylem, Pc = pericycle, Ph = phloem, Px = protoxylem, St = stele, SS = sclerenchyma sheath. Orig.