1) Genetic variations on tracheid microfibril angle of 55 Chinese fir clones were investigated.

2) The relation of tracheid and the density of wood were direct proportion.

3) The tracheid and sieve tube elements are all differentiated from the procambia in the center of the haustoria, and the former occurs prior to the latter.

4) Wood tracheid morphological features and their radial variation of Korean spruce plantations are studied and compared with those of natural forest.

5) Vessel and fibre - tracheid are both spiral thickening distinctly.

6) The variations of wood basic density and tracheid length, tracheid width, ratio of tracheid length and width of Pinus densiflora plantation in different stands were studied in this paper.

7) The results showed: from pith outward, the tracheid length and diameter and cell wall thickness of Taxodium ascendens wood with or without intermittent flood all increased.

8) A. yuanbaoshanensis showed great difference with other Abies species in tracheid diameter and rays height.

9) For the significant positively correlation exists between juvenile wood and mature wood in relative density and tracheid length, early selection for wood properties of Pinus massoniana is possible.

10) As planting density increased, the growth ring width and tracheid row decreased but proportion of late wood increased.

11) The effect of intermittent flood upon the radial variation of tracheid features of Taxodium ascendens was investigated.

12) The results are as follows: (1)The radial variation patterns of the tracheid morphological featues of the wood from plantation arc respectively similar to those from natural stand.

13) A kind of silicified fossil wood with mixed pits on the radial tracheid wall is described.

14) The volatile material increased in xylem after the PWN invaded. The blockage of water conduction caused by tracheid cavitation was very important factor causing the death of infected pine trees.

15) Microfibrillar angle within the S_2 layer of the secondary wall in tracheid decreases rapidly from pith outwards,[http:///tracheid.html] and then levels off after 13 years old.

16) Among the climatic factors which affect the geographic variation of tracheid morphological, moisture and rainfall are the principal factors, secondary is temperature.

17) The optimum selection age of basic density was determined at 10 years, the juvenile-mature correlation in tracheid length was unstable.

18) In this paper, 12 years old Chinese Fir clones were studied on the genetic variation of growth properties, basic density and tracheid morphological characteristics.

19) There are different types of pit-pair between the axial tracheids. the axial tracheid and the ray parenchyma, the axial tracheid and the ray tracheid.

20) The broken - line graph of average values of families show evident differences in wood basic specific gravity and tracheid length between different regions.