KEY TO THE FAMILIES. vii 



Calyx present. BETULACEAE, 76. 



Calyx not present. SALICACEAE, 72. 



Herbs (sometimes somewhat woody at base). 

 Leaves opposite. 

 Flowers perfect. 



Style 1. Isnardia, 169. 



Styles 2-5. CARYOPHYLLACEAE, 95. 



Flowers monoecious. 



Ovary 1-celled; stamens 2-5. URTICACEAE, 78. 



Ovary more than 1-celled; stamen 1. 



Ovary 4-celled. CALLITRICHACEAE, 157. 



Ovary 3-celled. EUPHORBIACEAE, 156. 



Leaves not opposite. 

 Flowers monoecious. 



Ovary 3-celled, 3-ovuled. EUPHORBIACEAE, 156. 



Ovary 1-celled, 1-ovuled. 



Flowers with scarious bracts. AMARANTHACEAE, 90. 



Flowers bractless or, if bracted, 



the bracts not scarious. CHENOPODIACEAE, 87. 



Flowers perfect or dioecious. 

 Pistils more than one. 



Stamens perigynous. ROSACEAE, 130. 



Stamens hypogynous. RANUNCULACEAE, 102. 



Pistil one. 



Ovary more than 1-celled. 

 Ovary 2-celled. 



Stamens 6. CRUCIFERAE, 113. 



Stamens 2. Synthyris, 124. 



Ovary more than 2-celled. 



Ovary 6-celled. ARISTOLOCHIACEAE, 81. 



Ovary 3-5-celled. AIZOACEAE, 91. 



Ovary 1-celled. 

 Ovary superior. 



Fruit an akene. POLYGONACEAE, 81. 



Fruit not an akene. CHENOPODIACEAE, 87. 



Ovary partly inferior. 



Flowers on a scape. Heuchera, 130. 



Flowers on a leafy stem. SANTALACEAE, 80. 



B. Petals Present. 



1. Stamens numerous, at least more than ten and more than twice the 

 sepals or calyx-lobes. 



Calyx free and separate from the ovary. 

 Pistils more than one. 



Ovaries cohering in a ring around a central 



axis. MALVACEAE, 162. 



Ovaries separate or, if united, not cohering 



in a ring around a central axis. 



Stamens perigynous. ROSACEAE, 130. 



Stamens hypogynous. 



Aquatic plants; leaves not dissected. NYMPHAEACEAE, 101. 

 Terrestrial plants or, if aquatic, the 



submersed leaves dissected. RANUNCULACEAE, 102. 



Pistil one, with one to several styles and stigmas. 



Leaves minutely punctate with pellucid dots. HYPERICACEAE, 163. 

 Leaves not punctate with pellucid dots. 



