July. 1920.] 



OGUBA -.—GROWTH IN THICKNESS. 



105 



Table X 



Height of ray 

 tissue in Cryptomeria in terms of 

 number of cells 



of individual cells might be somewhat 

 larger in outer rings than more central 

 ones. According to my measurements 

 in Cryptomeria, the absolute height of 

 ray cells was constant, the average 

 being 20 fi in all different parts. 



F. Xylem-elements in other kinds 

 of trees 



Tracheidal cells of coniferous wood 

 are the most suitable materials for the 

 study of variation of dimensions of 

 xylein-elements. On examining Pinus 

 densi flora fNo. XIV J and Tsuga diver si- 

 flora (No. XIII), I have got the similar 

 result as in Cryptomeria japonica ('Art. 

 Jap., p. (185), Table 26 1 ). Measure- 

 ments were made in the wood of 

 Chamaccyparis obutosa (No. XII) 

 about the variation of length and area 

 in cross sections of tracheids in differ- 

 ent ages and heights, as is shown in 

 the table XI and XII (H, height in '/veil' 2 ; Y, number of animal 

 rings counted from outside ; Length in mm., area in / 2 j. (Art. Jap., 

 p. (186), Table 27 and 28J. 



Dimensions of tracheids vary, according to aize and height, in 

 nearly the same way as we saw in Cryptomeria, but length and area 

 in cross sections of tracheids do not diminish beyond the maximum, 

 but remain almost constant. 



In the case of dicotyledonous wood, xylem-elements are not 

 uniform, and even within the same ring, the sizes of vessels are very 

 irregular, so that the result of their measurements will be very irregular 

 and complex. Sanio 3 measured the length of each element in a number 

 of dicotyledonous wood and got nearly the same result with regard to 

 the change of the length according to the age, as he got in pine, except 











A N 



j. IV 



B No. 



vnr 



X 



H 



* 



H 



5 



1— 6 



5 



1— 6 



15 



1— 9 



15 



1— 6 



30 



1—10 



35 



1— s 



' 



1—18 



50 



1-10 



70 



1— 25 



80 



1—17 







100 



1—21 







125 



1-25 







150 



1—26 







175 



1—26 







200 



1—24 









1-25 







250 



1—24 



1. A, Tsuga; B, Minus. 



2. 1 '.Ken'sCa. 1.8 m. . 



3. Sanio, C. (1873) Anatomie der gemein?n Kiefer, II— Jakrb. f. Wis 

 Bd. 9 



