MEASURE OF TOLERANCE. Ue 
MOST IMPORTANT SPECIES IN CENTRAL NEW YORK. 
[Beginning with the most tolerant. ] 
Ulmus americana (white elm). Quercus coccinea (searlet oak). 
Acer rubrum (red maple). Quercus velutina (yellow oak). 
Pinus strobus (white pine). Castanea dentata (chestnut). 
Quercus alba (white oak). Hicoria (hickories). 
Quercus platanoides (Swamp white Quercus prinus (chestnut oak). 
oak). Fraxinus americana (white ash). 
Quercus rubra (red oak). Juniperus virginiana (red cedar). 
In actual practice there is seldom any doubt as to the light re- 
quirements of the extreme members of the tolerance scale. The doubt 
comes with species which, under certain conditions of climate and soil, 
may be classed either as tolerant or intolerant. Instead of dividing 
species into “very tolerant,” “tolerant,” ‘“ intermediate,” ‘ intoler- 
ant,” and “ very intolerant,” it would therefore be more simple and 
practical to divide them into only three groups— tolerant,” “ par- 
tially tolerant,” and “intolerant.” This classification does not, how- 
ever, preclude the possibility of species with extreme requirements 
becoming, under certain conditions of climate and soil, partially 
tolerant. Thus, beech and fir, which are ordinarily very tolerant, 
on very poor soil and in a very cold climate may become only par- 
tially tolerant; and, on the other hand, pine and larch, which are 
ordinarily very intolerant, in most favorable soil and climate may 
become partially tolerant. 
To the group of tolerant trees belong the following genera: Taxus, 
Fagus, Abies, Picea, Tsuga, Pseudotsuga, Thuja, Avsculus, ever- 
green oaks and other evergreen broadleaf trees, and others. 
To the group of partially tolerant trees belong Carpinus, Tilia, 
Acer, Fraxinus, Ulmus, Alnus, the five-needled pines, Chamecypa- 
ris, Libocedrus, Sequotia, white oaks, and others. 
To the group of intolerant trees belong the black oaks; the two and 
three needled pines, such as Pinus contorta, P. jeffreyi, and others; 
Larix, Salix, Populus, Betula, Taxodium, Magnolia, Robinia, Lirio- 
dendron, and others. 
Of the secondary trees and arborescent shrubs, the evergreen broad- 
leaf shrubs, such as Buwus, are classed as tolerant; Corylus, Cornus, 
Ligustrum, Euonymus, Lonicera, and others are classed as partially 
tolerant; Prunus, Spartium, Calluna, Crategus, Viburnum, and 
others as intolerant. 
Of forest weeds, Polythrichum, Hypnum, Aspidium, Vaccimum, 
Hedera, and others are tolerant; Anemone and Pteris, partially tol- 
erant; Circium, Silene, Fragaria, and most of the grass and clover 
species, intolerant. 
‘90431 °—Bull. 92—11——4. 
