108 TEE BOTANICAL MAGAZINE. [Vol. xxxiv. No. «b. 



formula R 2 = PX r , where r and P are variable numbers, the value of 

 the former determining the type of the curve, and that of the latter, 

 the inclination of the curve. 



4. The most general type of radial curves is the case when r=l, 

 that is, R 2 = PX or 2? = V PX » which is the parabolic curve. In this 

 case, the area of wood in cross section produced every year is constant. 

 Large and old trees which I could hitherto observe showed the 

 parabolic radial curves. 



5. Thickness of annual rings produced in the same year varies 

 according to the height. In Cryptomeria, the maximum is at a height 

 of between 1—7 m., whence it decreases upwards and downwards. 



6. Though several authors found the close relation between the 

 amount of precipitation and the growth in thickness of trees, I could 

 not find any remarkable coincidence in this relation in Japanese trees, 

 except some extreme cases. 



7. Length of tracheids in the wood of Cryptomeria varies with 

 age. The rate of increase is greater in younger part, and becomes smaller 

 gradually, until the length reaches the maximum at the 150— 200th 

 annual ring, and from this point it decreases very slowly outwardly. 

 In Chamaecyparis, this maximum length continues through succeeding 

 rings. 



8. Length of tracheids also varies according to the height. At 

 the level between 3-11 m. it has the maximum value, and decreases 

 from this point upwards and downwards. 



9. In Cryptomeria, radial diameter of tracheids in cross section 

 in one and the same annual ring has its maximum at some distance 

 from the beginning of spring wood, passing outwardly to the com- 

 pressed summer wood elements with the minimum diameter. 



10. Area in cross section of tracheids of these two coniferous 

 trees also varies with age and height. The mode of variation is 

 similar to that of length. 



11. Height of ray tissue of coniferous wood, in terms of number 

 of cells, varies in the same way with the variation of length and area 

 of tracheids, with regard to age and height. 



12. In Cryptomeria each cell of ray tissue has vertkal height of 

 20 jut (in average) throughout all parts of the tree. 



13. In dicotyledonous -wood, there is the change of dimensions of 

 xylem-elements according to age, though it is not so marked as in 

 coniferous wood. 



14. Relative quantities of different xylem-elements change in 

 different annual rings, in the case of Quercus. 



