288 KNupSON: CAMBIUM DEVELOPMENT IN AMERICAN LARCH 
TABLE XI 
NUMBER OF ROWS OF XYLEM CELLS AND DIAMETER INCREASE OF XYLEM IN TREE E 
Diameter increase of No. June 6 
Region of cutting | No. May 22 Sylera May s2 
Diameter increase of 
xylem June 6 
Below rst whorl... re) — | 
Below 2d whorl ... 3 5 | ie a 
Below hor 5 on ai 7 139.5 u 
Below 4th whorl 4 £85. oe —— 
Below 5th whorl 4 88.8 u 9 | 256° 7 
Below 6th whorl... 7 185 yp 17 } 444 p 
Below 7th whorl...| 9 220.4 ub 20 | 48r yu 
AVeTage oii. 6558 5.8 139 FB g 286 fi 3g 
that except for the apical part of the trunk the growth there has 
been much greater than in the branches. The average diameter 
increase of xylem in all the branches was by May 22 only 10.7 up, 
and the average number of cells in the new xylem layer only 0.62. 
The greatest diameter increase in the branches was only 37 yp, 
while the average for the trunk was 5.8 cells with a diameter of 
139 u. If reference is made to TABLE vit it will be seen that no 
growth occurred in branch No. 2 while in the trunk at this region 
the increase was 55.5 u. The average diameter of xylem in 
branch No. 7 was only 4-5 p, while in the region of the trunk from 
which the branch was secured the diameter increase amounted to 
229 p. It is very evident, therefore, that in a larch of this age 
under isolated conditions growth does not begin first in the twigs 
and then extend to the trunk, but rather it begins first in the 
trunk. 
The figures in TABLE XI give no strong indication of the region 
in which growth first began. The diameter increase was greatest 
just below the 4th, 6th, and 7th whorls of branches. No increase 
was manifest near the apex. 
: TABLE XII 
Region of cutting No. of rows of xylem Dia. increase 
in trunk cells of xylem’ 
Below: 3st whorl. os syn Cutting lost 
Below 5th whorl............. 4 Itt pe 
Below 7th whorl. . 2... 202.6... 9 2224 
Below 9th whorl... .......... 5 129 u 
In order further to check the work of 1909 a few cuttings were 
made from another tree in the nursery row on May 22. This tree 
