KEY, BASED UPON FRUIT. 35 



d. Ovoid, oblong or ellipsoidal, surrounded at its base with an involucral cup 

 (Quercus), which is shallow, saucer-shaped and composed of 

 smooth, closely appressed scales 15. Q. RUBRA. 



(Id. Sharply 3-angled and in pairs, each pair invested with a 4-valved, dehis- 

 cent involucre composed of prickly scales (Fagus). 



16. F. FERRUGINEA. 



tldd. Short, club-shaped, surrounded with stiff hairs, tipped with the per- 

 sistent recurved style and arranged in globular heads (Platanus). 



13. P. OCCIDENTALS. 



CCCCC, Nut-like, but not invested with an involucre, globose, about as large as 

 peas and arranged in cymes with a large, leaf -like bract attached 



to each peduncle (Tilia) 3. T. AMERICANA. 



bb. Dehiscent Pericarp. 



c. Subglobose, coriaceous, dehiscent by 2-3 valves and containing one or very 

 few large seeds with smooth, shining coat and a large scar (Aes- 

 culus)', fruit prickly and leaves of 7 leaflets. 



6. AES. HIPPOCASTANUM. 



CC. Small, ovoid-lanceolate pods arranged in catkins, opening by two valves and 

 containing numerous seeds furnished with silky down (Populus). 



18. P. GRANDIDENTATA. 



(l(l. Aggregated Fruit composed of many carpels, either closed or open and 



cohering or closely massed together, forming a cone. 

 b. Scales of the cone open carpels (Coniferce). 



. Scales many, persistent and spreading at maturity, each subtended by a bract; 



ovules 2, inverted. 



d. Maturing the year after flowering (Pimts), ovate -conical, about 2 in. long, 

 smooth, carpellary scales slightly thickened at the apex, per- 

 sistent 19. P. RESINOSA. 



dd. Maturing the first season, the autumn after blossoming. 



e* Ovoid or oblong, 1-2 in. long, pendent; bracts inconspicuous; scales per- 

 sistent on the axis, thin and with eroded tip 20. ABIES NIGRA. 



ee. Ovoid, small, 8 lines or less, pendent, scales rounded and entire at tip. 



21. ABIES CANADENSIS. 

 eee. Cylindrical, large, 2-4 in., erect; bracts conspicuous, exserted; scales 



falling from the axis at maturity 22. ABIES BALSAMEA. 



eeee. Ovoid or roundish, small, 9 lines or less, scales persistent on the axis 



at maturity 23. LARIX AMERICANA. 



CC. Scales few, persistent, bractless; ovules 2-8, erect; cone oblong with oblong, 

 loosely imbricated scales somewhat thickened at the tip; seeds 



winged all round 24. THUJA OCCIDENTALS. 



bb. Scales 3-lobed bracts each subtending 2-3 closed, indehiscent carpels minia- 

 ture saniarse (Betula) 17. B. LDTEA. 



bbb. Scales closed carpels, growing from an elongated receptacle and consolidated 

 together. 



c. Dehiscent at maturity along the median line of the back, and letting out each 

 1-2 berry-like seeds suspended by extensile threads (Magnolia). 



1. M. ACUMINATA. 

 cc. Indehiscent at maturity and falling away as samarae. 



2. LlRIODENDRON TULIPIFERA 



