INDEX 
25 
References are to pages 
Nucleus — Continued 
of pleurococcus.304 
Nurses, care of bee larvae by . 46 
Nuthatches, at suet station . . 118 
destroyers of Lepidoptera . 42 
useful birds.114 
Nutrients, defined.13 
Nutrition a fundamental func¬ 
tion . 5 
Nuts, from hardwood trees . . 351 
furnished by walnut family . 297 
indehiscent fruits .... 237 
Nymphs of cicada.33 
O 
Oak leaf.297 
trees. 352, 364 
Oat plant, root system of . . 252 
Oats, a cereal .... 244, 295 
a monocotyledon .... 227 
member of grass family . . 295 
types of heads of .... 389 
Obesity cures.504 
Obnoxious plants, names of 301 
Octopus, example of mollusk 185, 191 
Odonata, order of insects . . 29 
Odor, use of, in flowers . 199 
Odors of other foods absorbed 
by milk.316 
produced by fermentation . 211 
Oils, tests for.228 
Oils, a class of foods .... 416 
Old age, a period in life history 402 
Olfactory lobes, function of . • 89 
of frog ..88 
One-celled plants.364 
Onions, storage of food in . 379 
Operculum of fish.71 
Opium, a poison . . . 487, 506 
Optic lobes of frog.88 
Optic nerve.474 
Oral side of starfish . . . 170 
Orange, exapaple of berry . 233 
Orbits, defined.472 
Orchard fruits from rose family 298 
Orchids, greenhouse epiphytes . 373 
roots of.253 
Organ, defined. 6 
part of body. 7 
system. 7 
Organic foods.410 
matter, example of ... . 10 
Organism, beginning of new . 6 
study of. 8 
sensation in. 6 
Organs, defined. 7 
of circulation of fish ... 75 
of crayfish.63, 64 
of earthworm .... 180-182 
of frog.85-89 
of plants.195 
of respiration in man . . . 444 
Organ system, defined ... 7 
part of body. 7 
Orioles, food of.42 
nest of.112 
Orthoptera, order of insects . . 29 
Osmosis, defined.15 
in absorption of food . . 414 
in photosynthesis .... 282 
in root hairs.248 
in sponges.156 
Outer coat of pollen grain 208 
Outer ear.475 
Outer skeleton, of crayfish . . 61 
of turtle.100 
Ovary, of ccelenterates . 165 
of frog.87 
part of pistil.198 
Overeating, results of ... 504 
Overwork predisposes to tu¬ 
berculosis .497 
Oviducts of frog.87 
Ovipositor of grasshopper . . 24 
Ovules, change to seed in . . 219 
described.212 
of pine.344 
Owl, feet and beak of. . 108, 109 
screech, beneficial . . . . 115 
snowy, a winter visitant . . 112 
Oxalis .291 
Oxen.132 
Oxidation, defined.12 
in birds.109 
Oxygen, a chemical element 12 
a condition for the growth-of 
bacteria.310 
proportion of, in living things 13 
test for ....... 281 
use in respiration .... 5 
use of, by birds.HO 
