xxx 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 Polygonaceae 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 12 



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 



