14 PLANTS OF YELLOWSTONE NATIONAL PARK 
41. Leaves toothed but not lobed. 42. 
42. Pistils 5. Spiraea lucida ___(p. 74) 
42. Pistil only 1. 43. 
43. Corolla attached above the ovary. Serviceberry ( Amelanchier) _(p. 78) 
43. Corolla attached below the ovary. Black chokecherry (Prunus melano- 
carpa )___ ------(p. 78) 
44. Plants without green leaves. 45. 
44. Plants with green leaves. 50. 
45. Stem flat, fleshy, and prickly. Pricklypear (Opuntia polyacantha) _(p. 88) 
45. Stem not flat, fleshy, and prickly. 46. 
46. Plants parasitic on pine trees. Mistletoe (Arceuthobium americanum) _(p. 47) 
46. Plants not parasitic on pine trees. 47. 
47. Plants not at all hairy. Coralroot ( Corallorhiza )___ ____(p. 44) 
47. Plants somewhat hairy. 48. 
48. Plants 10 to 60 inches high. Pinedrops (Pterospora andromedea )_(p. 96) 
48. Plants less than 10 inches high. 49. 
49. Petals united. Western ghostpipe (Thalesia fasciculata) ___(p. 113) 
49. Petals distinct. Pinesap (Hypopitys multiflora) ___ __(p. 96) 
50. Aquatic plants. 51. 
50. Plants not strictly aquatic though some may grow in very wet places. 61. 
51. Plant body a minute, floating thallus without true stems or leaves. Duck¬ 
weed ( Lemna) ____(p. 36) 
51. Plants with stems and leaves. 52. 
52. Flowers conspicuous. 53. 
52. Flowers very small and inconspicuous. 57. 
53. Flowers pink. Water ladysthumb (Polygonum amphibium) _ ,_(p. 52) 
53. Flowers white. 54. 
53. Flowers yellow. 55. 
54. Leaves arrow-shaped. Arrowhead (Sagittaria cuneata) _ ____(p. 33) 
54. Leaves much dissected. Water crowfoot (Batrachium) ___(p. 61) 
55. Leaves large and entire. Wokas (Nymphaea polysepala) _(p. 56) 
55. Leaves lobed or dissected. 56. 
56. Leaves bearing small bladders. Bladderwort ( Utricularia )_(p. 113) 
56. Leaves without bladders. Ranunculus purshii _ ,____ __(p. 62) 
57. Leaves in whorls. 58. 
57. Leaves alternate. 60. 
57. Leaves opposite. Waterstar (Callitriche palustris) _(p. 85) 
58. Flowers wholly under water. Hornwort (Ceratophyllum demersum) _(p. 57) 
58. Flowers, or some of them, on stalks above the water. 59. 
59. Leaves entire, in whorls of 6 to 12. Marestail (Hippuris vulgaris) p. 93) 
59. Leaves dissected, in whorls of 3 to 5. Parrotfeather (Myriophyllum) _ _ (p. 94) 
60. Flowers perfect. Pondweed (Potamogeton) _(p. 31) 
60. Flowers imperfect. Leaves long and narrow. Bur-reed (Sparganium) 
(p. 29) 
61. Stems flat, fleshy, and prickly. Pricklypear (<Opuntia polyacantha) (p. 88) 
61. Stems not flat, fleshy, and prickly. 62. 
62. Plants grasslike or rushlike. Flowers not conspicuously colored. 63. 
62. Plants not grasslike or rushlike or if so the flowers colored and conspicuous. 
67. 
63. Plants 3 to 6 feet tall. Flower clusters about 1 inch thick and 4 to 12 inches 
long. Cattail ( Typha) _________ ,__(p. 26) 
63. Plants smaller. Flowers in much smaller clusters. 64. 
64. Flowers enclosed by chafflike bracts. 65. 
64. Flowers not enclosed by chafflike bracts. 66. 
