"Fig.8.2. Types of successive cambial activity. The products of a primary thickening meriste are a series of prodesmogen strands that may produce very little (e.g. <i>Pisonia</i>), or much more (<i>Atriplex'</i>) secondary xylem. Origin of first primary thickening meristem may be from cortex, or from parenchyma yielded to outside by desmogic cambium. Origin of second (and subsequent) primary thickening meristems is from parenchyma derived from desmogic cambia. Middle row: various centrifugal types."
S Carlquist (1988)
S Carlquist (1988) p.259 Fig. 8.2. "Chapter 8. Cambial Variants (Anomalous Secondary Growth)". In: <i>Comparative Wood Anatomy</i>. Part of the series <i>Springer Series in Wood Science</i>. Springer Verlag Berlin Heidelberg.