Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 64. (Budapest 1972)

Kováts, D. ; Stieber, J.: Some observations on the dynamism of structural development in the stem-borne root of Lithospermum purpureo-coeruleum L.

Fig. 2. Schematic cross-section pictures of several cm long, old Lithospermum purpureo-coeruleum L. stem-borne roots, at subsequent levels a-m. Root diameters and their increase (similarly as in the preceding Figure), the stressing of the central cylinder and omission of cortex were taken into account in the drawings: a-b-c. Diarchal, triarchal and tetrarchal structures observable at levels adjacent to root apex, medially with a still undifferentiated procambium bundle, phloem bundles alternating with xylem bundles, waved cambium already evolving, endoderm Caspary-punctate (-striate), externally with rhizoderm; c-h. See Fig. 3; h. tetrarchal procambium differentiated, waved cambium closed into a ring, elements of first secondary xylems appearing, endoderm usually still Caspary-punctate (-striate), rhizoderm present ; i. secondary xylem already predominating, usually cell walls of endoderm also incrassate, rhizoderm still present ; i/1. also roots were observed which at this developmental level were already covered with exoderm, in contrast with the preceding one, but whose epiderm was still Caspary-punctate (-striate); j. compact xylem cylinder already evolved at upper levels, endoderm usually following xylem in becoming secondary, but externally rhizoderm still present; k. xylem cylinder compact, endodermal cell walls incrassate, exoderm also externally; 1. primary cortex separated, root covered by secondary epiderm in. an already sclerotic pith present in upper levels near shoot, primary bundles discernible, root covered by nruftiseriate periderm; 1. primary xylem, 2. secondary xylem, 3. phloem, 4. cambium, 5. primary and Casparypunctate (-striate) endoderm, 8. exoderm, 9. periderm, 10. sclerotic pith. The procambium is fascicular also here, but its differentiation deviates from that observed in the roots of the seedlings (KOVÁTS, 1971). By the enclosing into a ring of the waved cambium and the production of secondary xylem, the xylem