KEY, BASED UPON FLOWERS. 



ft. 2 Dioecious, calyx deciduous, leaves deciduous; involucre none 



(Sassafras) 32. S. OFFICINALE. 



gr. 2 Anthers extrorse ; stigma 2-cleft ; fruit a 

 h. Samara, 1 -celled and winged all round (Ulmus). 



i. Flowers nearly sessile ; samara not c ilia te-f ringed ; leaves 



very rough above 11. U. FULVA. 



i 2 . Flowers on drooping pedicels ; samara ciliate- fringed ; leaves 

 smooth. 

 Bud-scales glabrous ; flowers fascicled ; branches not 



corky-winged . . 33. U. AMERICANA. 



Bud-scales downy ciliate ; flowers racemed ; branches 



corky- winged 34. U. RACEMOSA. 



ft 2 . Capsule, dry, nut like, not winged (Planera). 



114. P. AQUATICA. 



g\ Anthers introrse ; fruit a dark-purple drupe , leaves long- taper- 

 pointed 12. CELTIS OCCIDENTALIS. 



</ 4 . Anthers laterally dehiscent ; fruit a drupe. 



111. FORESTIERA ACUMINATA. 



Flowers diclinous and one or both sorts in catkins. 

 . Only one sort (the staminate flowers) in catkins. 



e. Fertile flowers single or clustered ; fruit naked ; leaves pinnately com- 

 pound (Juglandaceoe) . 



f. Corolla present in the fertile flowers ; fruit with valveless epicarp 

 (Juglans) . 



g. Fruit ovid-oblong and viscid-hairy 14. J. CINEREA. 



</ 2 . Fruit globose, roughly dotted (not viscid-hairy). 



35. J. NIGRA. 

 / 2 . Corolla not present in the fertile flower ; fruit with usually 4-valved 



epicarp (Carya) which is 

 g. Thick ; valves separating to base ; bark 

 ft. In loose plates ; leaflets 



5, smoothish ; nut small 36. C. ALBA. 



7-9 ; nut large 64. C. SULCATA. 



ft 2 . Close, leaflets 7-9, tomentose 90. C. TOMENTOSA. 



g-. Thin ; bark close ; nut 

 ft. Quite smooth, small, thin-shelled, leaflets 



5-7 ; kernel edible 91. C. MICROCARPA. 



7-9 ; kernel very bitter 37. C. AMARA. 



ft 2 . More ridged, larger, thicker- shelled ; leaflets 5-9. 



65. C. PORCINA. 



ft 3 . Rugose, angular ; leaflets 11-13 115. C. AQUATICA. 



e 5 . Fertile flowers 1-3 together, invested wholly or partly with an invol- 



ucral covering ; leaves simple (Cupuliferce). 



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

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

 aments 



g. Pendulous (section Lepidobalanus); stigmas 

 ft. Sessile or nearly so and dilated ; stamens 6-8; abortive ovules 

 mostly basal (subsec. Leucobalanus, WHITE OAKS) ; matura- 

 tion 



i. Annual : nut glabrous inside; abortive ovules basal; 

 J. Leaves falling in autumn, 

 Jc. Sinuate-pinnatifid. 

 I. Obovate-oblong, pale below and with 



m. Narrow oblique lobes 38. Q. ALBA. 



m 2 . Wide lobes, less oblique and margin of lobes 



Undulate- toothed 160. Q. LOBATA. 



Entire or nearly so 136. Q. GARRY ANA. 



V. Obovate with deep sinuses and the central pair of lobes 



usually wide and spreading 93. Q. OBTUSILOBA. 



7c, Lyrate-pinnatifid ; nut or more immersed. 



"Peduncles shorter than petioles . . .39. Q. MACROCARPA 



Peduncles longer than petioles 66. Q. BICOLOR. 



fc 3 . Coarsely undulate-crenate-toothed (CHESTNUT OAKS) 



