﻿Trees of Xcw York IStafc 69 



TWIG KEY TO THE SPECIES 



PAGE 



1 . Foliage persistent through the winter 2 



1. FoHage deciduous 19 



2. Leaves J of an inch or less in width 3 



2. Leaves h of an inch or more in width 17 



3. Leaves in fascicles of 2-5 4 



3. Leaves opposite or in spirals 10 



4. Leaves in fascicles of 5; fascicle-sheaths deciduous Pinus Strobus 77 



4. Leaves in fascicles of 2 or 3 ; fascicle-sheaths persistent 5 



5. Leaves in fascicles of 3 6 



5. Leaves in fascicles of 2 7 



6. Leaves flexible ; foliage bluish green ; buds obtuse Pinus echina a 85 



6. Leaves rigid; foliage yellowish green; buds acute Pinus rigida 79 



7. Leaves 3 or more inches long 8 



7. Leaves not over 3 inches long 9 



8. Leaves serrulate Pinus resinosa 87 



8. Leaves entire Pinus echinata 85 



9. Leaves f-l§ mches long, serrulate, flexible; buds acute Pinus wginiana 81 



9. Leaves lj-3 inches long, entire, rigid; buds obtuse Pinus Banksiana 83 



10. Leaves in spirals, linear or acicular 11 



10. Leaves opposite, awl-shaped or scale-like 15 



11. Leaves 4-angled, stomatiferous on all sides; foliage with a prickly feel 12 



11. Leaves flattened, with two stomatiferous lines below; foliage without prickly 



feel 14 



12. T^^-igs glabrous Picea canadensis 91 



12. Twigs pubescent 13 



1 3. Foliage bluish green Picea mariana 95 



13. Foliage yellowish green Picea rubra 93 



14. Leaves sessile, in falling leaving circular scars Abies balsamea 97 



14. Leaves jointed to short persistent stergimata, in falling lea\'ing a raised 



scar Tsuga canadensis 99 



15. Sprays not flattened Juniperus virginiana 105 



15. Sprays flattened, branches appearing as in one plane 16 



16. Fohage bluish green; leaves I/I6-5 of an inch long 



Chamaecyparis thj'oide 101 

 16. Foliage yellowish green; leaves 1/5-j of an inch long. .Thuja occidentalis 103 



17. Leaves undulate, with a few spinose teeth Ilex opaca 287 



17. Leaves entire-margined 18 



18. Leaves 3-4 inches long, flat; midribs impressed above.. . .Kalmia latifolia 323 

 18. Leaves 4-11 inches long, the margin revolute; midribs rounded above. . . 



Rhododendron maximum 321 

 19. Leaf-scars densely clustered on short lateral spurs or scattered and strongly 



decurrent on twigs of the season Larix laricina 89 



19. Leaf-scars alternate, opposite or whorled 20 



20. Leaf -scars opposite or whorled 21 



20. Leaf-scars alternate 37 



21. Bimdle-scars in a closed or nearly closed longitudinal ellipse; leaf -scars 



orbicular 22 



21. Bundle-scars in a lunate or V-shaped line, distinct or confluent 23 



22. Ellipse open at the top; pith diaphragmed Paulo wnia tomentosa 335 



22. Elhpse closed at the top; pith homogeneous except at the nodes 



Catalpa speciosa, 339 

 Catalpa bignonioides 337 



23. Buds sticky-resinous; twigs stout Aesculus Hippocastanum 303 



23. Buds not sticky-resinous; twigs slender or stout 24 



24. Bundle-scars one or more, nearlj^ confluent forming a single line 25 



24. Bundle-scars 3 or in 3 distinct groups 29 



25. Leaf-scars not connected by a transverse line ; terminal buds lacking 



Rhamnus cathartica 305 



