METHODS OF DETERMINING TOLERANCE. 33 
lative activity only in intense light. Assimilation means, in every 
case, growth, and therefore it is natural to expect a similar difference 
in the capacity of growth of shade-enduring and light-needing species. 
It is known experimentally that if hght-needing and shade-enduring 
species are raised in full hght, the most rapid growth of the young 
seedlings will be found among the light-needing species, but if the 
two kinds of seedlings are raised open shade, the result will be the 
reverse. It is known further that in older trees also there is a direct 
relationship between the capacity for height growth and the toler- 
ance of the species; the more light needing the species the more rapid 
is its growth. Otherwise a slow-growing but light-needing species 
would not be able to compete with other more tolerant species. 
Comparison between species, arranged in order of their tolerance and 
rapidity of growth, brings out clearly this relationship: 
Tolerance and rate of growth. 
ACCORDING TO GAymR (1898). 
Rapidity of growth. (Most rapid growing 
Tolerance. (Most intolerant first.) first.) 
Larig europea (European larch). Larig europea (Huropean larch). 
Pinus sylvestris (Scotch pine). Pinus sylvestris (Scotch pine). 
Picea (spruce). Picea (spruce). 
Abies pectinata (silver fir). Abies pectinata (silver fir). 
Betula (birch). Betula (birch). 
Populus tremula (aspen-poplar). Populus tremula (aspen-poplar). 
Fraxvinus excelsior (Huropean ash). Alnus incana (hoary alder). 
Quercus (oak). Acer (maple). 
Almus incana (hoary alder). Fraxinus excelsior (Huropean ash). 
Ulmus effusa (elm). Tilia (linden). 
Tilia (linden). Ulmus effusa (spreading elm). 
Acer (maple). Quercus (oak). 
Carpinus betulus (European horn- Carpinus betulus : (European horn> 
beam). beam). 
Fagus (beech). Fagus (beech). 
ACCORDING TO Hyer (1898). 
Rapidity of growth. (Most rapid growing 
Tolerance. (Most tolerant first.) first.) 
Larig europea (Kuropean larch). Lariz europea (European larch). 
Pinus sylvestris (Scotch pine). Pinus sylvestris (Scotch pine). 
Picea (spruce). Picea (spruce). 
Abies (fir). Abies (fir). 
Populus tremula (aspen-poplar). Populus tremula (aspen-poplar). 
Betula (birch). Betula (birch). 
Alnus incana (hoary alder). Alnus incana (hoary alder). 
Acer (maple). Acer (maple). 
Uimus effusa (spreading elm). Ulmus effusa (Spreading elm). 
Acer pseudoplatanus (sycamore maple). Acer pseudoplatanus (sycamore maple). 
Quercus (oak). Tilia (linden). 
Carpinus . betulus (Huropean horn- Quercus (oak). 
beam). Carpinus betulus (HKuropean horn-. 
Tilia (linden). beam). 
Fagus (beech). Fagus (beech). 
