KNUDSON: CAMBIUM DEVELOPMENT IN AMERICAN LARCH 287 
in the middle branches. This increase corresponds with the re- 
sults secured previously on the diameter increase in the trunk, 
in which it was found that the growth first began in the middle 
region. 
In regard to the second question as to the region of the branch 
in which growth first occurs, TABLE X is suggestive. The figures 
of the following table are the averages of the seven apical cuttings, 
the seven basal cuttings and the average diameter of xylem in the 
middle regions of the seven branches. 
TABLE X 
AVERAGE DIAMETER INCREASE OF XYLEM AT APEX, MIDDLE, AND BASE OF ALL LATERAL 
‘CHES 
Region of Diameter increase 
cutting of xylem 
PGE oo ceria pis os oon pe ee RN RE eee a ER area jet as 20.8u 
Mitidle 5 ae a ris Me EO Oh per oes 7.5 pe 
Basal 2 205.2b i es Fae a ee, i ae ea 2.5 
From previous results it was expected that the growth would 
first occur in the middle of the branch, but the evidence indicates 
that the development of xylem in the lateral branches begins at 
the apex and then continues towards the base. The opening of 
the buds, however, does not follow the same order. On April 26, 
1911, the lateral branches of a tree in the nursery row were ex- 
amined and it was found that buds on the one and two years old 
wood had not yet opened, on the third year wood the leaves were 
just protruding while on the older wood the buds were fully opened. 
In regard to the third question, “‘ Does diameter increase in 
the twigs and branches precede that in the trunk?” the folldwing 
observations were made. From the same tree from which the 
- cuttings from the lateral branches were removed and on the same 
day,—namely, May 22, cuttings were removed from the apex to 
the base of the trunk. Seven such cuttings were removed from 
the south side of the tree, one cutting just below each whorl of 
branches. From a study of slides prepared from the material the 
following figures have been obtained. (See TABLE x1.) There 
are also included in TABLE XI figures derived from cuttings made 
on June 6. 
A comparison of the figures for May 22 with the figures for 
growth in the lateral branches (see DIAGRAM ut) reveals the fact 
