12 PLANTS OF YELLOWSTONE NATIONAL PARK 
KEY TO THE COMMON SEED PLANTS, FERNS, AND FERN 
ALLIES OF YELLOWSTONE NATIONAL PARK 
1. Plants without seeds or true flowers. Spore producing. 2. 
1. Seed producing plants. 5. 
2. Plants with jointed stems and no evident leaves. Horsetail family_(p. 19) 
2. Leafy plants. 3. 
3. Mosslike plants with small leaves; spores of one kind. Clubmoss family, (p. 20) 
3. Mosslike plants with small leaves; spores of two kinds. Selaginella 
family_ _________(p. 21) 
3. Water plants with grasslike leaves. Quillwort family_ ______ _(p. 20) 
3. Land plants with branched or lobed leaves. 4. 
4. Fruit bodies (sporangia) borne on specialized branches. Adder’s tongue 
family_ _______ _(p. 17) 
4. Fruit bodies borne on the lower surfaces or margins of the leaves. Fern 
family________ (p. 17) 
4. Fruit bodies borne at base of leaves on short stalks. Pepperwort 
family________(p. 19) 
5. Woody plants (trees and shrubs). 6. 
5. Non-woody plants. 44. 
6. Trees. 7. 
6. Shrubs. 13. 
7. Evergreen trees with needlelike or scalelike leaves. Pine family_(p. 21) 
7. Broad-leaved plants; not evergreen. 8. 
8. Leaves opposite. Dwarf maple (^4cer glabrum) ____(p. 85) 
8. Leaves alternate. 9. 
9. Bark pale or light colored. 10. 
9. Bark dark. 12. 
10. Bark rough. Narrowleaf cottonwood ( Populus angustifolia) _(p. 46) 
10. Bark smooth. 11. 
11. Petiole flattened. Quaking aspen {Pojpulus tremuioides) _(p. 46) 
11. Petiole not flattened. Balsam poplar ( Populus balsamifera) _(p. 46) 
12. Buds with several overlapping scales. Bark of branches marked by hori¬ 
zontal slits. Birch (Betula) ____(p. 47) 
12. Buds with only 1 or 2 scales. Bark of branches not marked by horizontal 
slits. Mountain alder ( Alnus tenuifolia) _ (p. 47) 
13. Parasitic on pine trees. Mistletoe ( Arceuthobium americanum) __(p. 47) 
13. Not parasitic on pine trees. 14. 
14. Leaves evergreen. 15. 
14. Leaves not evergreen. 19. 
15. Leaves awl-shaped, or scalelike. Juniper ( Juniperus )_(p. 26) 
15. Leaves not awl-shaped or scalelike. 16. 
16. Leaves small, linear, crowded; fruit a dry capsule. Red mountainheath 
(Phyllodoce empetriformis )_(p. 97) 
16. Leaves small, oval; fruit berrylike. Western wintergreen ( Gaultheria 
humifusa )___(p. 97) 
16. Leaves broad and not crowded. 17. 
17. Leaves opposite. Rocky Mountain kalmia ( Kalmia polifolia )_(p. 97) 
17. Leaves alternate. 18. 
18. Leaves toothed, hollylike. Creeping hollygrape ( Berberis repens) _(p. 63) 
18. Leaves entire, not hollylike. Bearberry ( Arctostaphylos uva-ursi) __ (p. 98) 
19. Leaves opposite. 20. 
19. Leaves alternate. 23. 
20. Leaves compound. Elder ( Sambucus )___(p. 115) 
