Key to the Genera xxix 



2. Branches columnar; seed dark CEREUS, p. 324. 



2. Branches jointed; seed pale OPUNTIA, p. 325. 



3. Leaves scalelike, feathery; fruit a capsule. . .TAMARIX, p. 308. 

 3. Trees appearing leafless; southwestern 4 



4. Twigs with black, cushion-like processes. . CANOTIA, p. 293. 



4. Twigs without cushion-like processes 5 



5. Twigs with lateral spines; fruit a legume DALE A, p. 266. 



5. Twigs terminating in a spine ; fruit a berry 



KOEBERLINIA, p. 321 . 



B. LEAVES LOBED 



1. Leaves 4-lobed; bud large with valvate scales; fruit an aggregate 

 of samaras LIRIODENDRON, p. 235. 



1 . Leaves not 4-lobed ; bud scales not valvate 2 



2. Leaves entire or 1-2 lobed, all types usually present; aromatic; 



fruit a blue drupe on red stalk SASSAFRAS, p. 239. 



2. Leaves more than 2-lobed, not strongly aromatic 3 



3. Leaves palmately 3-7 lobed; fruit in multiple heads 4 



3. Leaves not palmately 3-7 lobed; fruit not in heads 5 



4. Leaves finely toothed; terminal bud scaly; twigs with corky 

 wings; fruit of capsules LIQUIDAMBAR, p. 241. 



4. Leaves coarsely toothed ; terminal bud absent, lateral enclosed 

 in enlarged leaf petiole; fruit of achenes; bark characteristically 

 mottled PLAT ANUS, p. 243. 



5. Terminal bud absent; sap milky; fruit a berry-like multiple 

 of drupes 6 



5. Terminal bud present ; sap watery ; fruit simple 7 



6. Leaves velvety-hairy below; fruit globose, orange 



BROUSSONETIA, p. 227. 



6. Leaves smooth to hairy below; fruit ovoid, purple, dark red, 

 or white MORUS, p. 227. 



7. Twigs with sharp thorns; fruit a small, red pome 



CRATAEGUS, p. 253. 



7. Twigs unarmed (sometimes spinescent in Malus) 8 



8. Leaf scars with many bundle traces ; fruit an acorn 



QUERCUS, p. 1 74. 



8. Leaf scars with 3 bundle traces 9 



9. Leaves toothed; fruit a pome; buds small MALUS, p. 244. 



9. Leaf lobes entire; fruit a capsule; buds large . . POPULUS, p. 120 



C. LEAVES ENTIRE 



1. Leaves, twigs, and drupes silvery scurfy 2 



1 . Plants not silvery scurfy 3 



2. Leaves elliptic to oblong SHEPHERDI A, p. 329. 



2. Leaves lanceolate ELAEAGNUS, p. 329. 



3. Leaves heart-shaped; fruit a legume CERCIS, p. 273. 



