I wish to thank the Department of Conservation for the opportunity of doing this work. Key to the Families. PAGE Leaves linear or scale-like. Pinaceæ 19 Leaves not as above. A. Leaves compound. Leaves palmately compound. Æsculaceæ 251 Leaves without an odd leaflet at the end. Cæsalpinaceæ 226 Leaves with an odd leaflet at the end. Leaves alternate. Leaflets toothed all around. Juglandaceæ 52 Leaflets entire, or with 1-4 teeth near the base. Trees with thorns, leaflets entire, generally less than 4 cm. (1-1/2 inches) long. Fabaceæ 233 Trees without thorns, leaflets entire or with 1-4 teeth near the base, generally longer than 4 cm. (1-1/2 inches). Simarubaceæ 237 Leaves opposite. Leaflets 3-5, fruit in pairs. Aceraceæ 239 Leaflets 5-11, fruit single. Oleaceæ 267 A. Leaves simple. Leaves opposite or whorled. Petioles more than 4 cm. (1-1/2 inches) long. Blades palmately 3-5 lobed. Aceraceæ 239 Blades entire or with 1 or 2 lateral lobes. Bignoniaceæ 284 Petioles less than 4 cm. (1-1/2 inches) long. Flowers 4-parted, stone of fruit round. Cornaceæ 259 Flowers 5-parted, stone of fruit flattened. Caprifoliaceæ 288 Leaves alternate. B. Leaves entire. Trees with thorns and a milky sap. Maclura in Moraceæ 155 Trees without thorns, sap not milky. Leaves 3-5 nerved at the base. Leaves 3-nerved at the base. Celtis in Ulmaceæ 146 Leaves 5-nerved at the base. Cercis in Cæsalpinaceæ 227 Leaves with 1 primary nerve. Leaves usually more than 1.5 dm. (6 inches) long, flowers solitary. Flowers appearing before or with the leaves. Anonaceæ 161 Flowers appearing after the leaves. Magnoliaceæ 155 Leaves less than 1.5 dm. (6 inches) long, flowers in clusters. Bark and leaves aromatic Lauraceæ 163