Mould, black. See "_Mucorini_." blue. See "_Penicillium_." herbarium. See "_Eurotium_." insect. See "_Entomophthoreæ_." water. See "_Saprolegnia_." Mountain-fringe, 192. Mountain-laurel, 210; Fig. 116. _Mucor_, 55. mucedo, 56; Fig. 32. _Mucor stolonifer_, 55-56. general structure, 55. structure of filaments, 55. spore cases, 55. sexual spores, 56. _Mucorini_, 54. Mulberry, 183. Mullein, 217; Fig. 120. _Musa_, _-aceæ_. See "Banana." _Musci_. See "True mosses." Mushroom, 82. Mustard, 192. _Mycomycetes_. See "True fungi." _Myosotis_. See "Forget-me-not." _Myristica_, _-ineæ_. See "Nutmeg." _Myrtifloræ_, 205. Myrtle, 205, 206. _Myrtus_. See "Myrtle." _Myxomycetes_. See "Slime-mould." _Naias_. See "Pond-weed." _Naiadeæ_, 159. Narcissus, 146. Nasturtium, 197, 227. _Navicula_, 42; Fig. 24. Nectar, 225. Nectary, 186. Nelumbo, 189, 190; Fig. 101. _Nelumbieæ_, 190. _Nemophila_, 214. _Nepenthes_, _-eæ_. See "Pitcher plant." _Nesæa_, 206. Nettle. See "_Urticinæ_." _Nicotiana_. See "Tobacco." Night-blooming cereus, 204. Nightshade, 215; Fig. 119. _Nitella_, 40. _Nitelleæ_, 40. Node, 39. Nucleus, 7, 31, 231. Nuclear division, 7, 31, 231; Figs. 127, 128. Nucleolus, 7, 231. Nutmeg, 188. _Nyctagineæ_, 183. _Nymphæa_, 189; Fig. 101. _Nymphæaceæ_, 190. Oak, 183, 225; Fig. 97. _Œdogonium_, 26-28; Fig. 16. reproduction, 27. fertilization, 28. resting spores, 28. _Œnothera_. See "Evening primrose." Oil-channel, 202. _Oleaceæ_. See "Olive." Oleander, 219. Olive, 218. _Onagraceæ_, 206. _Onoclea_, 104; Fig. 70. Oögonium, 27, 36, 39, 45, 59, 62. Oöphyte, 109. Opium--opium poppy, 191. _Ophioglosseæ_. See "Adder-tongue." _Ophioglossum_, 116. _Opuntia_. See "Prickly pear." _Opuntieæ_, 203. Orange, 198. Orchid, 164, 166, 227; Figs. 89, 90. _Orchideæ_, 164. _Orchis_, 227; Fig. 89. Organic bodies, 1. Origanum oil, 234. _Oscillaria_, 15, 16; Fig. 6. movements, 15. color, 16. structure and reproduction, 16. _Osmunda_. See "Flowering-fern." Ostrich-fern, 104-109. germination of spores, 104. prothallium, 104, 105. archegonium, 105, 106. antheridium and spermatozoids, 106. fertilization, 107. embryo and young plant, 107, 108. comparison with sporogonium of bryophytes, 109. Ovary, 129, 148, 156, 202. Ovule, 129, 131, 144, 148, 151, 179. _Oxalis_. See "Wood-sorrel." _Oxydendrum_, 211; Fig. 116. Oxygen, 2, 95. Palea, 161. Palisade parenchyma, 178. Palm, 157. date, 159. coco, 159. _Palmæ_. See "Palm." Palmate, 171. Palmetto, 159. _Pandaneæ_, 159. _Papaveraceæ_. See "Poppy." Papaw, 186; Fig. 100. _Papilionaceæ_, 208. Pappus, 223. _Papyrus_, 161. Paranucleus, 231. Parasite, 54. Parenchyma. See "Soft tissue." _Parmelia_, 73, 75; Fig. 44. Partridge-berry, 223, 228. _Passiflora_. See "Passion-flower." _Passiflorinæ_, 205. Passion-flower, 204; Fig. 112. Pea, 207, 208; Fig. 115. Peach, 206. Pear, 206. _Pediastrum_, 23; Fig. 11.