Gum. See "_Eucalyptus_." _Gymnocarpæ_, 84. Gymnosperm, 129, 141. _Gymnosporangium_, 79-81; Fig. 47. cedar apples, 79. spores, 80. _Gynandræ_, 153, 164. Gynœcium, 148, 167. Gynostemium. See "Column." _Habenaria_, 166, 227; Fig. 90. Hæmatoxylin, 233. Hair, 8, 177. _Haloragidaceæ_, 206. Hazel, 182, 183, 225; Fig. 97. Head, 181. Heath, 211. _Helobiæ_, 153, 167. _Hemerocallis_. See "Day lily." _Hemi-angiocarpæ_, 84. Hemlock, 142; Fig. 78. Hemp, 183. _Hepaticæ_. See "Liverwort." Hermaphrodite, 199. Heterocyst, 17. Heterostylism, 228. _Hibiscus_, 195. Hickory, 170, 183. Holly, 199. Hollyhock, 195. Honey locust, 209. Honeysuckle, 170, 172, 181, 223; Fig. 124. Hop, 171, 181; Fig. 97. Horned pond-weed, 224. Horse-chestnut, 170, 199. Horse-tail, 116-120. field, 120-122; Fig. 72. stems and tubers, 120. fertile branches, 120. leaves, 121. cone, 121. stem, 121. sporangia and spores, 121. sterile branches, 121. histology of stem, 121. of sporangia, 122. spores, 122. germination, prothallium, 122. Hound's-tongue, 215; Fig. 119. _Houstonia_, 223; Fig. 124. _Hoya_. See "Wax-plant." Huckleberry, 181, 211; Fig. 116. Humming-bird, 226. Hyacinth, 146. _Hydnum_, 84; Fig. 51. _Hydrangea_, _-geæ_, 202; Fig. 111. _Hydrocharideæ_, 167. Hydrogen, 2, 95. _Hydropeltidinæ_, 189. _Hydrophyllum_, _-aceæ_. See "Water-leaf." _Hypericum_, _-aceæ_. See "St. John's-wort." _Ilex_. See "Holly." _Impatiens_. See "Jewel-weed," "Balsam." India-rubber, 200. Indian-pipe, 144, 210; Fig. 79. Indian turnip. See "_Arisæma_." Indusium, 118. Inflorescence, 157. Integument, 133, 144, 151, 180. Intercellular space, 124, 135, 150. Internode, 39. Iodine, 4, 22, 31. _Ipomœa_, 213. _Iridaceæ_, 156. Iris, 154, 156; Fig. 84. Irish moss, 49. _Isocarpæ_, 210, 212. _Isoetes_. See "Quill-wort." _Iulifloræ_, 181. Ivy, 202. Jack-in-the-pulpit. See "_Arisæma_." Jasmine, 218. _Jeffersonia_. See "Twin-leaf." Jewel-weed, 197; Fig. 107. Joint fir, 140, 142. _Juncagineæ_, 167. _Juncus_. See "Rush." _Jungermanniaceæ_, 92; Fig. 57. _Kalmia_. See "Mountain laurel." Karyokinesis, 233. Keel, 208. Kelp. See "_Laminaria_." giant. See "_Macrocystis_." Knotgrass. See "_Polygonum_." Labellum. See "Lip." _Labiatæ_. See "Mint." _Labiatifloræ_, 215. Lady's-slipper, 164, 166, 198; Fig. 90. Lamella, 83. _Laminaria_, 45, 47; Fig. 28. _Lamium_. See "Dead nettle." Larch. See "Tamarack." _Larix_. See "Tamarack." Larkspur, 186, 227; Fig. 99. Latex, 191. Laurel, 188. _Laurineæ_. See "Laurel." Lavender, 215. Leaf-green. See "Chlorophyll." Leaf tendril, 171. Leaf thorn, 172. _Leguminosæ_, 207. _Lemanea_, 53; Fig. 31. _Lemna_. See "Duck-weed." Lemon, 198. _Lentibulariaceæ_, 217. Lettuce, 223. _Lichenes_, 73; Figs. 44, 45. Ligula, 127. _Ligulatæ_, 125. Lilac, 170, 181, 218. _Liliaceæ_, 155. _Liliifloræ_, 153, 155; Fig. 83. _Lilium_. See "Lily." Lily, 146, 155. Lily-of-the-valley, 155.