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 litter 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 



