I A Outlines of leaflets with two or three teeth at base. Ailanthus IA Outlines of leaflets serrate { Sumacs (except Poison sumac) { Mountain ashes { Walnuts { Hickories I A C Leaflets oval, apex obtuse Locusts (except Honey locust) I A C Leaflets oblong, apex acute Poison sumac I B Outlines of leaflets entire Ashes (except Mountain ashes) I B Outlines of leaflets serrate Ashes (except Mountain ashes) I B Leaflets irregularly or coarsely toothed, 3-lobed or nearly entire Box elder J Irregularly bi-pinnate, outlines of leaflets entire, thorns on stem and trunk Honey locust LIST OF PLATES. PLATE PAGE I. Larix Americana 4 II. Pinus Strobus 6 III. Pinus rigida 7 IV. Pinus Banksiana 9 V. Pinus resinosa 11 VI. Picea nigra 14 VII. Picea rubra 16 VIII. Picea alba 18 IX. Tsuga Canadensis 20 X. Abies balsamea 22 XI. Thuja occidentalis 24 XII. Cupressus thyoides 26 XIII. Juniperus Virginiana 28 XIV. Populus tremuloides 30 XV. Populus grandidentata 32 XVI. Populus heterophylla 34 XVII. Populus deltoides 35 XVIII. Populus balsamifera 37 XIX. Populus candicans 39 XX. Salix discolor 41 XXI. Salix nigra 43 XXII. Juglans cinerea 47 XXIII. Juglans nigra 49 XXIV. Carya alba 51 XXV. Carya tomentosa 53 XXVI. Carya porcina 55 XXVII. Carya amara 57 XXVIII. Ostrya Virginica 58 XXIX. Carpinus Caroliniana 60