xx INTRODUCTION 



(n) Stamens usually 8; style and 



stigma 2 SAXIFRAGACEAE 191 



n. Sepals 5 



(m) Stamens numerous ; styles 3 EUPHORBIACEAE 34 

 (n) Stamens 6-8; stigmas 2-3 POLYGON ACEAE 51 

 (y) Ovary inferior; aquatic herbs GUNNERACEAE 206 



2. Sepals absent, or occasionally very minute 



a. Woody plants 



(1) Leaves scale-like or needle-like, usually 

 evergreen 



(a) Stems jointed, low and shrubby; scales 



papery GNETACEAE 369 



(b) Stems not jointed, mostly trees; leaves 



green, usually needle-like PINACEAE 364 



(2) Leaves not scale-like or needle-like, de- 

 ciduous 



(a) Leaves simple, alternate 



x. Fruit with many hairy seeds; flowers 



dioecious SALICACEAE 72 



y. Fruit 1 -seeded ; flowers usually monoe- 

 cious BETULACEAE 220 



(b) Leaves compound, opposite OLEACEAE 99 



b. Herbs 



(1) Flowers in heads, surrounded by 5 petal- 



like glands EUPHORBIACEAE 34 



(2) Flowers not in heads with petal-like glands 



(a) Flowers in spikelets with papery scales; 



leaves grass-like 



x. Flower enclosed in 2 scales; stem hol- 

 low, round POACEAE 335 



y. Flower with a single scale; stems solid, 



mostly triangular CYPERACEAE 324 



(b) Flowers not in spikelets with papery 



scales 



x. Plants small floating leaf-like disks LEMNACEAE 315 



y. Plants with leafy stems 



(x) Leaves in whorls of 6-8 CERATOPHYLLACEAE 



9 



(y) Leaves not in whorls of 6-8 

 m. Leaves parallel-veined 



