=. 
iM 
The Struggles for Existence. 135 
tween the two; while exhibiting a remarkable capacity of vege- 
tating in the shade, they are really light-needing species but 
comparatively slow growers and long lived. One and the same 
species behaves also somewhat differently under different soil 
and climatic conditions; for instance, as a rule the light-needing 
species can endure more shade on moist soils and the shade 
enduring require more light on drier soils. 
In the earliest stages of life the little seedlings of most trees 
require partial shade and are quite sensitive in regard to light 
conditions. Some have such a small range of light and shade 
endurance that, while there may be millions of little seedlings 
sprouted, they will all perish if some of the mother trees are not 
removed and more light given; and they will perish equally if 
the old growth is removed too suddenly and the delicate leaf 
structure, under the influence of direct sunlight, is made to ex- 
ercise its functions beyond its capacity. 
Left to itself, as the forest grows up and as the individual 
trees develop, each trying to hold its ground and struggling for 
light, a natural thinning takes place, some trees lagging behind 
in growth and being shaded out, until in old age only as many 
trees remain as can occupy the ground without incommoding 
each other. 
This struggle among the individuals goes on during their en- 
tire life. Some few shoot ahead, perhaps because of a stronger 
constitution or some favorable external cause, and overtower 
their neighbors. These, lagging behind, fall more and more 
under the shading influence of their stronger neighbors until 
entirely suppressed, when they only vegetate until they die. 
The struggle continues, however, among the dominant class and it 
neverends. For as Hercules the unconquerable succumbed to the 
poison that penetrated to his bones, so does the mighty giant of 
the forest fall a prey to the insidious work of rot and fungus and 
insects. When its heart is riddled and weakened, first the dry 
branches crumble and gradually give opportunity for the young 
aftergrowth of shade-enduring kinds, patiently waiting for light, 
to strengthen; then break the large limbs and the dry top, and 
after having weathered the onslaught of the storms for centuries 
and the euerillas of the fungus tribe for decades, finally the giant 
falls, with its decaying substance enriching the soil for future 
generations. Into the breach rush the young epigones, each 
struggling to supplant its progenitor. 
19—Nar. Groac. Maa., von. VI, 1894. 
