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. 3. Various phases of differentiation of the tetrarchal procambium bundle observed in older roots. Means of differentiation marked by arrows, its several phases by subsequent letters of the alphabet. Types of differentiation : ch-cdh-cdgh-cgh-cch-cfeh-cfgh-cfh. Hatched parts indicating already differentiated proto- and metaxylem parts of pro£ambial bundle. becomes a closed ring (Fig. 1. h; Plate IV., Figs. 25-27). The greater part of the xylem is already secondary when the endoderm also tends to become secondary by the incrassation of its cell walls. In these cross-section levels we still find rhizoderm, in many cases even when this root-haired zone originates directly from the cortex level of the shoot covered with cystolithic hairs. By the increasing amount of secondary xylem, the entire xylem cylinder rounds off (Fig. 1. i-1; Plate V., Figs. 39, 40). The wall of the parenchymatous cells of the central pith thickens (sclerotizes) with simple pits (Plate III., Fig. 17, Plate VI, Figs. 45-47). The division by anticlinal walls in the cells of the pericambial zone sets off the separation process of the primary cortex (Plate V., Fig. 40, Plate VI, Figs. 41-44). In the roots studied, the primary cortex peels off in many cases covered with the