KEY, BASED UPON FLOWERS. 3 



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



16. FAGUS FERRUGINEA. 



eee. Fertile flowers in sliort catkins; nuts small and acheniuni-like; sterile 

 flowers destitute of calyx; leaves simple. 



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



ff. Nutlet not inclosed but subtended by an enlarged leafy bract. 



42. CARPINUS CAROLINIANA. 

 dd. Both staminate and pistillate flowers in catkins. 



e. 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). 

 f. Trees with white bark and ovate leaves doubly serrate; veins hairy 



beneath; fertile catkins drooping 43. B. PAPYRACEA. 



ff. Trees with yellowish bark; leaves short-petioled, smoothish; fertile 



catkins short and erect 17. B. LUTEA. 



fff. Trees with reddish-brown bark; leaves cordate-ovate; fertile catkins 



suberect 44. B. LENTA. 



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



hairy tuft (Salicacece). 



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

 kins peduncled, expanding with the leaves in late spring. 

 ff. Ovaries pedicillate and glabrous; scales greenish-yellow, deciduous, 

 stamens mostly 5; leaves lance-linear, tapering at each end. 



45. S. NIGRA. 

 ffff. Ovaries sessile and glabrous; stamens 2; leaves lanceolate, tapering 



both ways; branches yellow 46. S. ALBA var. VTTELLINA. 



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



8-30, leaves broad (Populus). 

 ff. Branchlets terete. 



h. Leaves roundish ovate with large unequal sinuate teeth. 



18. P. GRANDIDENTATA. 



hh. Leaves ovate, acuminate, finely serrate, whitish and reticulate- 

 veined beneath 47. P. BALSAMIFERA. 



ffff. Branchlets slightly angular, leaves broadly deltoid. 



48. P. MONOLIPERA. 



a a. Gymnospermae seeds naked, borne superficially on carpellary scales. Cone- 



bearing (Coniferm). 

 b. Scales of cone many, each in the axil of a bract and bearing 2 inverted ovules; 



seeds winged. 

 c. Leaves evergreen, fascicled; cones maturing the second year (Pinus). 



(1. Leaves in 2s with long sheaths; cones about half as long as the leaves 



and with scales thickened at the apex but unarmed. .19. PINUS RESINOSA. 



(Id. Leaves in 3s with short sheaths; cone about half as long as the leaves 



and with scales thickened at the apex and armed with a reflexed spine. 



49. P. RIGIDA. 

 ddd. Leaves in 5s with very short sheaths; cones longer than the leaves and 



with scales not thickened at the ends, unarmed 50. P. STROBUS. 



cc. Leaves evergreen, scattered (not fascicled); cones with thin scales, maturing 



the first year (Abies). 

 d. Cones erect, cylindrical, large (3-4 in.) and with conspicuous bracts; leaves 



flat, linear 22. A. BALSAMEA. 



dd. Cones pendent and bracts inconspicuous. 



. Small, 8 lines or less, scales entire at tip; leaves linear. 



21. A. CANADENSIS. 



ee. Larger, 1-1| in., scales eroded at tip; leaves 4-angled 20. A. NIGRA. 



CCC. Leaves deciduous, soft, needle-shaped and in fascicles of many each; cones 

 about 8 lines ill length, scales thin (Larix) and with inflected margins. 



23. L. AMERICANA, 

 bb. Scales of cone few, without bracts and each bearing 2-8 erect ovules. 



c. Flowers monoscious; scales of the oblong cone dry and divergent at maturity; 



leaves evergreen THUJA OCCIDENTALIS. 



cc. Flowers dioecious; scales fleshy and consolidated, making a small, dark blue, 

 berry -like fruit; leaves scale-like and imbricated in 4 rows. 



25. JUNIPERUS VlRGINIANA. 



