m. Trunk fluted; fruit inclosed within 
mm. Trunk not fluted; fruit not in- 
closed within a halberd-shaped 
involucre. 
n. Bark of trunk gray-brown, brok- 
en into narrow, flattish pieces 
loose at the ends; fruit in hop- 
like strobiles...OSTIRYA, p. 81. 
nn. Bark of trunk white, yellow or 
dark brown, platy or cleaving off 
in papery layers; fruit not in 
hop-like strobiles ........ eset 
aamewene ne wee 4S BETULA, p. 84. 
kk. Leaf-blades almost as broad as they 
are long. 
1. Lower side of leaves more or less 
downy; sap milky; leaves not crowded 
on short, spur-like branchlets; fruit 
: berry-like, black..... MORUS, p. 135. 
ll. Lower side of leaves glabrous; sap 
not milky; leaves crowded on short, 
spur-like branchlets; fruit a large, 
green pome ......... PYRUS, p. 142. 
ee. Margin of leaves distinctly lobed. 
f. Fruit an acorn................ QUERCUS, p. 96. 
ff. Fruit not an acorn. 
g. Leaves fan-shaped, with many fine veins radiat- 
ing from the base of the blade..GINKGO, p. 3. 
gg. Leaves not fan-shaped, without many fine veins 
radiating from the base of the blade. 
h. Leaf-lobes ‘entire. 
i. Leaf-petioles 5-6 inches long; leaves lustrous 
above; twigs not aromatic, when bruised.... 
dee huenwas aeaNes LIRIODENDRON, p. 137. 
ii. Leaf-petioles about 1 inch long; leaves dull 
above; twigs spicy-aromatic when bruised 
Sladi lacete tacos sale oR eiats SASSAFRAS, p. 130. 
hh. Leaf-lobes sinuate-toothed to serrate. 
— XxIV — 
