THE EASTERN HEMLOCK. 23 
The shallow roots of hemlock are extremely sensitive to drying out 
of the surface soil, which in part accounts for the death of trees ex- 
posed to increased light, as when a road is cut through the woods, or 
near-by trees are removed in lumbering. 
In mountainous regions hemlock usually occupies the cool, moist, 
northerly and easterly slopes, coves, benches, and sides of ravines, 
often reaching the edges of streams, but avoiding extremely wet and 
swampy places. On north and east slopes of ridges it often ascends 
to the crest, and may grow along the edges of rocky cliffs and bluffs. 
In New Hampshire it ranges from near sea level to about 2,400 feet, 
but in Georgia and Alabama it is not found below an elevation of 
about 800 feet, and reaches this level only in cool and humid situa- 
tions. 
REPRODUCTION. 
Hemlock is a prolific seed bearer, but reproduces poorly. Trees 
receiving a moderate amount of light begin to bear seed when from 
30 to 50 years old. As a rule seed is produced abundantly every 
two or three years, but ordinarily only from 30 to 60 per cent of the 
seeds are fertile. The cones mature in a single season, and the seeds 
fall from them during the late autumn and winter, germinating in the 
spring, from March to the end of May. On account of their small 
size and their large, membranous wings, the seeds may be borne con- 
siderable distances by the wind. They will germinate and take root 
in poorly drained situations, on moss-covered logs and decayed stumps 
as well as in fresh, mineral soil; but the best seed bed is a moist, well- 
decomposed leaf Utter in which the seeds become completely buried. 
Too much or too little shade will kill hemlock seedlings. For this 
reason reproduction is rarely found either under the heaviest shade 
of the parent trees or in clearings and burned-over areas, but is 
usually abundant in the more open portions of the hemlock forest 
or under the lighter shade of hardwoods or pine in mixture. If the 
water in the soil is not stagnant, more seedlings will survive in very 
moist than in relatively dry situations. The seedlings grow best 
when in deep, moist layers of mellow decaying leaves and twigs 
overlying fresh but well-drained loamy soils. The decay of the 
leaves and twigs breaks down their chemical structure and releases 
various food materials for the seedling hemlock. These materials 
become available largely or only through the agency of certain 
fungi, called mycorrhiza,*which exist as felted layers of fine, thread- 
like mycelium, completely inclosing and even penetrating the root- 
lets. Many of the threads extend out into the mass of decaying 
humus, and through these the products of decay are conducted from 
the decomposing leaves to the felt, and thence into the rootlets, 
where they become serviceable for nutrition and growth. It is 
