KEY, BASED UPON FLOWERS. 3 



e*. Fertile flowers 1-3 together, invested wholly or partly with an involucral 



covering; leaves simple (Cupulifera). 

 f. Involucre valveless, cup-like, composed of many scales and only partly 



inclosing the one nut, i. e., acorn (Quercus). 



g. Leaves with teeth and lobes obtuse or rounded (not bristle-pointed); 



acorns maturing first year (and hence on new wood) and leaves 



Oblong, sinnate-pinnatifid, nut immersed in the tubercled cup. 



38. Q. ALBA. 



Lyrate pinnatifid, nut or more immersed... .39. Q. MACROCARPA. 

 Obovate, sinnate-crenate, nut immersed, peduncles longer than 



petioles 66. Q. BICOLOR. 



Oblong, undulately crenate-toothed, peduncles shorter than peti- 

 oles . . .67. Q. PRINUS. 



Lanceolate-oblong, sharply undulate-toothed; acorns small. 



68. Q. MUHLENBERGII. 



f/ 2 . Leaves with teeth and lobes acute and bristle-pointed; acorns matur- 

 ing the second year (and hence on old wood); leaves 

 Moderately pinnatifid; cup very shallow and saucer-shaped; scales 



fine 15. Q. RUBRA. 



Deeply pinnatifid; cup top-shaped; scales rather coarse; nut half 



immersed 69 . Q. COCCINEA. 



/ 2 . Involucre 2-4-valved, becoming hard and prickly and inclosing 1-3 

 sweet, edible, flattened, subglobose nuts; sterile flowers in catkins. 



40. C AST AN E A VESCA. 

 /' 3 . Involucre 4-valved and inclosing two 3-cornered, edible nuts. 



16. FAGUS PERRUGINEA. 



e 3 . Fertile flowers in short catkins; nuts small and achenium-like; sterile 

 flowers destitute of calyx; leaves simple. 



/. Nutlet inclosed in a bladder-like bag 41. OSTRYA VIRGINICA. 



/ 2 . Nutlet not inclosed but subtended by an enlarged leafy bract. 



42. CARPINUS CAROLINIANA. 



2 . Both staminate and pistillate flowers in catkins. 

 e. Ovary and pod 2-celled, many-seeded. 



60. LlQUIDAMBAR STYRACIFLUA. 



e 2 . Ovary 1-2 celled with a single ovule in each cell; 



/, Calyx scale-like or none; stigmas 2, filamentous; fertile flowers arranged 

 2 or 3 together under each scale of the cone-like catkin (Betula); bark 



g. Brown and close, catkins erect 44. B. LENTA. 



</'. Yellowish-gray and ragged, catkins sub-erect 17. B. LUTEA. 



. g 3 - White, and leaves. 



Deltoid, smooth both sides 70. B. POPULIFOLIA. 



Ovate, hairy on veins beneath 43. B. PAPYRACEA. 



/*. Calyx regular and succulent in fruit 63. MONUS RUBRA. 



e 3 . Ovary 1-celled and many-seeded, the seeds at maturity furnished with a 



hairy tuft (Salicacem). 



f. Bracts of the catkins entire; calyx wanting; stamens 2-7 (Salix); cat- 

 kins on leafy branchlets with yellowish, deciduous scales; capsules 

 glabrous; stamens 3-5; petioles 

 g. Glandular;' scales of catkin entire; leaves 



Narrow- lanceolate; fruiting catkins rather dense. . . .45. S. NIGRA. 

 Lanceolate or ovate lanceolate, glaucous beneath, fruiting catkins 



very loose 71 . S. AMYGDALOIDES, 



Not glandular; scales dentate 46. S. ALBA. 



Bracts of the catkins lacerately fringed ; calyx a disk-like cup; stamens 



8-30, leaves broad (Populus); styles with 



ff. Narrow lobes; capsule small; seeds minute, petioles laterally com- 

 pressed; leaves 



Cordate-orbicular, finely serrate 72. P. TREMULOTDES. 



Ovate-orbicular, coarsely dentate 18. P. GRANDIDENTATA. 



Deltoid; branchlets terete 73. P. DILATATA. 



g 2 . Broad lobes; capsules large; seeds 1 line or more in length and 

 leaves 



Ovate, reticulated and whitish beneath 47. P. BALSAMIFERA. 



Broadly deltoid; branchlets angled 48. P. MONILIFERA. 



