KEY,, BASED UPO:^ FLOWERS. 



dd. Ovary superior free from the calyx. 



e. Stipules sheathing the stem; trees with naked monoecious flowers ar 



ranged in heads 13. PLATANUS OCCIDENTALS. 



ee. Stipules not sheathing the stem or none. 

 /. Ovules a pair in each cell of the ovary which becomes in 



y. Fruit a double samara; leaves simple and palmately veined (Acer). 

 h. Flowers appearing with the leaves in pendulous corymbs (not sub- 

 sessile) 7. A. SACCHARINUM. 



hh. Flowers appearing before the leaves in short umbels. 



26. A. DASYCARPUM. 



gg. Fruit a 1-celled and 1-seeded samara (Fraxinus); flowers dioecious; 

 calyx persistent at the terete base of the suniara; corolla none; 

 leaflets stalked. 

 h. Branchlets and petioles glabrous; leaflets entire'or nearly so. 



10. F. AMERICANA. 



hh. Branchlets and petioles velvety pubescent. . . .81 .F. PUBESCENS. 

 ff. Ovules single in each of the 1 or 2 cells of the ovary. 



g. Anthers opening by uplifted valves; stigma single and entire; flowers 



dioecious; stamens 9; anthers 4-celled; involucre none; fruit an 



ovoid blue drupe with reddish pedicel. .32. SASSAFRAS OFFICINALE. 



gg* Anthers extrorse; stigma 2-cleft; fruit a 1-celled samara winged all 



. round ( Ulmus). 

 h. Flowers nearly sessile; samara not fringed; ciliate; leaves very 



rough above 11. U. FULVA. 



hh. Flowers on drooping pedicels; samara ciliate-f ringed; leaves 

 smooth. 



Bud-scales glabrous; flowers fascicled; branches not corky- 

 winged 38. U. AMERICANA. 



Bud-scales downy-ciliate; flowers racemed; branches croky- 



winged 34. U. RACEMOSA. 



ggg. Anthers introrse; fruit a dark purple drupe; leaves long-taper- 

 pointed 12. CELTIS OCCIDENTALIS, 



CC. Flowers diclinous and one or both sorts in catkins. 

 d. Only one sort (the starninate flowers) in catkins. 



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

 pound (JuglandacecK). 



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

 (Juglans}. 



</, Fruit ovate, oblong and viscid-hairy 14. J. CINEREA. 



gg. Fruit globose, roughly dotted (not viscid-hairy) 35. J. NIGRA. 



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



epicarp (Gary a). 

 ff. Nut small and edible, depressed globular, shell hard, valves of the 



epicarp thick and distinct to base 36. C. ALBA. 



gg. Nut bitter, subglobose, shell tender, valves half united, sutures 



prominent 37. C. AMARA. 



ee. Fertile flowers 1-3 together invested wholly or partly with an involucral 



covering; leaves simple (Cupuliferce). 

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



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



g. Acorns maturing the first year, sessile, leaves with rounded lobes. 

 h. Nut immersed in the tubercled cup; leaves deeply sinnate-pinna- 

 tifid, oblong in outline and with obtuse rounded lobes. 



38. Q. ALBA. 



hh. Nut deeply immersed (half or sometimes quite entirely) in a cup 

 composed of distinctly imbricated and hard pointed scales which 

 form a fringe about its margin; leaves lyrate-pinnatifid most 



deeply in the middle 39. Q. MACROCARPA. 



gg. Acorns maturing the second year; nut^ immersed in a shallow cup 

 composed of fine, closely appressed scales; leaves moderately 



pinnatifid and with 7-9 awn-pointed lobes 15. Q. RUBRA. 



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

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



40. CASTANEA VESCA. 



