18 
KEY TO THE FAMILIES 
Flowers 1 in the axil of each bract; calyx none. 
Fruit a 1-celled capsule with many downy seeds. 
Salicaceae, p. 53. 
Fruit a waxy-coated berry-like nut with 1 seed.. 
Myricaceae, p. 70. 
Flowers 2 or 3 in the axil of each bract; calyx present; 
fruit a very small seed-like nut... 
Betulaceae, p. 70. 
Staminate flowers in catkins, the pistillate solitary or clustered. 
Fruit a nut enclosed in a leafy tubular involucre... 
CORYLACEAE, p. 71. 
Fruit a nut set in a scaly cup or bur (acorn or chestnut). 
Fagaceae, p. 71. 
Leaves pinnately compound; fruit a nut. Juglandaceae, p. 69. 
B. Flowers not in catkins. 
1. Trees, shrubs or woody climbers. 
Leaves opposite. 
Trees; leaves pinnate. 
Stamens 4 or 5 ; fruit a double samara. Aceraceae, p. 74. 
Stamens commonly 2; fruit a simple samara. Oleaceae, p. 125. 
Woody climbers; stamens numerous; sepals 4, petal-like. 
Clematis, p 
.Leaves alternate and simple. 
Trees or shrubs. 
Flowers in ball-like clusters ; calyx none. Platanaceae, p 
Flowers not in ball-like clusters; calyx present. 
Stamens 4 to 9. 
Sap not milky. 
Fruit a samara. Ulmaceae, p. 60. 
Fruit not a samara. 
34. 
88. 
Fruit a berry ; stamens 4 or 5; anthers opening 
lengthwise. Rhamnaceae, p. 75. 
Fruit a drupe ;stamens 9; anthers opening by 
valves. Lauraceae, p. 35. 
Sap milky; fruit an aggregate fruit. Moraceae, p. 61. 
Stamens many to numerous. 
Fruit a tailed achene; ovary superior. ; . 
Cercocarpus, p. 92. 
Fruit a capsule; ovary inferior or partly inferior. 
Myrtaceae, p. 108. 
Woody climber; stamens 6, anthers sessile. Aristolochia, p. 60. 
2. Herbs; ovary superior (except Asarum and Aizoaceae). 
a. Calyx and corolla both wanting. 
Stamens and pistils in same flower; flowers in a spike, each flower sub¬ 
tended by a colored bract, the spike subtended by a conspicuous 
colored involucre. Saururaceae, p. 59. 
