NM/D 
Fic. 1.—Northern limits of tree species represented by lines having identification numbers and marks: 0, original; r, revised; isobars outlined by connected dots and 
average yearly temperature indicated in degrees; 1, Picea mariana; 2, P. canadensis; 3, Larix americana; 4, Populus balsamifera; 5, Betula papyrifera; 6, Populus tremu- 
loides 7, Pinus Banksiana; 8, P. Banksiana (other data and outliers); 9, Abies canadensis; 10, Thuja occidentalis; 1oA, Ulmus americana; 11, Pinus Strebus; 12, Betula 
lutea; 13, Acer Saccharum; 14, Quercus rubra; 15, Tsuga canadensis; 16, Fagus americana; 17, Juglans cinerea; 18, Carya amara; 19, Juglans nigra; 20, Castanca dentata. 
