KNUDSON: CAMBIUM DEVELOPMENT IN AMERICAN LARCH 283 
TABLE VII 
TOTAL NUMBER OF NEW ROWS AND DIAMETER OF PHLOEM, CAMBIUM 
IN TREES B AnD D 
Nov. 13 | Mays «| Mayxixz May 25 June 8 June 18 
Region of cutting Fa tags eee ER d 3 ; 
se No. ae No.| sir | No. res | No. i No. ce 
Below 1st whorl....| 6 | 34 |— 75| 8 | 68 |36 | 612/60 |1,231 
Below 2d r .|6| 34 | 6| 34] 9| 58/12 | 89 |57 | 840) 70 [1,544 
Below 3d whorl 6 | 34 | 9 | 68.120 | 88 (0-3) 9S 1,680 
Below 4th whorl 6 | 34 |10} 102/10] 102 |16 {143 {53 {1,071} 70 {1,520 
Below 5th whorl aad dee | ea eo | Ss NTA hs ire a ee re 1,486 
Below 6th whorl 6 | 34 |10| 68/15} 108|18 (147 | 48 |1,040/65 |1,506 
Below 7th whorl 6 | 34 |—| — bs ae Birt Be S| eg ieee i af foams BR 8g 
Below 8th whorl OG 5421085 pea toe ae 92 | 48 so 
Below oth whorl....| 6 | 34 8 61 —| — /|12 76 |44 | 955/68 (1,537 
Below 1oth whorl...| 6 | 34 | 9) 75 —!|— |— |— |— | — |62 {1,530 
Average . hee eee OL Ba 9! 72 11! 901 12.6 'TO1.5 ATS | 917! 69.4'1,508 
The season of diameter growth in larch is relatively short. 
Practically all of the growth occurred during the month of June. 
The small increase produced from the time of bud opening, April 
19 to May 25, consisted entirely of cambium and phloem develop- 
ment. The diameter increases of trees A and C and B and D 
during the season 1909 are graphically represented in DIAGRAM II. 
INVESTIGATION OF IQII 
Since the studies made in 1909 indicated that growth in 
diameter first occurred in the middle region of the trunk and not 
at the base or apex, it seemed advisable to continue these studies 
with respect to the development in the lateral branches. The 
investigation was made with the object of answering the three 
following questions: (1) Does inception of diameter increase begin 
first in the topmost branches, in the middle, or in the basal, 
branches? (2) In what part of the individual branches does 
diameter increase begin? (3) Does xylem development in the 
lateral branches precede that in the trunk? 
For this investigation a larch tree of approximately Io years 
of age was used. It was growing isolated, about 100 feet from 
the trees mentioned above, growing in the nursery row. For con- 
venience this tree is hereafter designated as tree E. On May 22, 
from each of the whorls of branches from apex to base, one branch 
