Secondary xylem is the wood part of stem, root and branch of a tree excluding the primary xylem and their pith.
This book gives detailed descriptions that the secondary xylem keeps its elaborative process, but the main body
of the wood part of a standing living tree vitality in is non-living biomaterial.
It is firstly realized by this project that the static wood differences within an individual tree can serve
as an experimental material to study the dynamic change during the elaborative process. That is the
crossing between life science and material science. Hence, this project has broken through the long-term
academic limit related to wood formation in botany and wood science within the range of cell division, maturation,
and deposition process of the substances of cell walls. The life nature and the changeable state of
secondary xylem during its lasting elaboration have been an academic blank. This is an
important but unknown part of wood formation mechanism. This book is the original research
findings of the basic theory about secondary xylem development. Growth sheath and the independence of two directional growths are defined and paid
attention for the first time as two characters of a tree's growth in this project. On the basis of the facts of secondary xylem development and the needs for the study on it,
some new concepts and measurements adopted in this project are as follows: two directional ages and their combination, special requirement for the sampling positions within a sample tree and the necessary types of the diagram that correspond with the mathematical principles. It is testified by the experimental results of the lasting life change determined from non-living wood material that the change during the secondary xylem elaboration is under geneti control, and it is theoretically ascertained that the nature of the change is development.