DURATION OF LEAVES IN EVERGREENS , I5I 
Sargent (14) and Sudworth (17), about 3 years. Observations seem 
to indicate that the leaves of mature trees have a greater duration 
than those of sapHngs; that leaves in the shade have a greater duration 
than those in the open ; that a dry climate seems to prolong the duration 
of the leaves; that a bog habitat has the same effect as a dry climate. 
Leaves remain on the tree for at least two or three years after losing 
their green color, and then are gradually sloughed off by the increase 
in size of the twig. Sudworth and Sargent also agree in saying that 
the lateral branchlets, which are shed entire, fall in their second year. 
The writer found that the duration of lateral branchlets also varies 
with habitat. Full data were not taken, but observations showed 
that under typical moisture conditions their duration was 2 to 3 
years, while in bog specimens they persisted 4, 5 or 6 years {figs. 11,12). 
9. Tsuga heterophylla Sarg. Shortest leaf duration observed, 2 
years; average, 4-7 years; extreme, 12 years. In general, mature 
trees show a greater leaf duration than do saplings under the same 
conditions of light and moisture. However, the shaded saplings 
observed in the vicinity of Seattle showed a greater leaf duration than 
that of mature trees growing under the same conditions. The saplings 
observed grew on fallen logs in dense shade under the parent trees, 
and had grown very slowly. Specimens which showed 20 annual 
growth-rings were less than a meter high, and no thicker than an 
ordinary lead pencil. The linear growth per year in many of the twigs 
examined was less than a centimeter, the needles on each year's 
growth were few in number, and the individual leaves were very small. 
There may be some correlation between this extreme slowness of 
growth and the increased duration of the leaves. Saplings in a moist 
climate show a longer leaf duration than saplings in a dry climate, 
while the converse is true for mature trees. 
Bog saplings, observed in the peat bog at Ronald, Washington, 
were dwarfed and stunted in their growth to a much greater extent 
than the shaded saplings previously described. As determined by 
counting the annual rings under the low power of the compound micro- 
scope, these saplings ranged in age from 5 to 32 years. They were 
from 17 to 60 cm. high, but the height was not proportional to the 
age. Both lateral and terminal shoots averaged less than a centimeter 
per year in linear growth ; and a year's growth in many cases comprised 
from 6 to 10 needles, which were much below normal in size. The 
leaf durations in these bog saplings show a remarkable feature, which 
