INDEX 19 
References < 
are to pages 
Houses, source of materials for 
261 
Immovable joints . 
434 
How fertilization is accom- 
Immunity 
plished. 
212 
defined and discussed . 
. 
516 
How tracts can be reforested . 
356 
Immunization .... 
513 
How the smoker’s heart is 
Imperfect flowers, kinds . 
204 
affected. 
482 
of corn. 
204 
Howard, Dr. L. 0. 
525 
Importance of muscles 
437 
Human biology. 
399 
Importation of certain fruits for- 
Human progress. 
521 
bidden. 
524 
Humming birds, beak of . . . 
109 
Improving the varieties 
of 
summer residents .... 
112 
plants and animals . 
424 
Humor, aqueous. 
473 
Incisor teeth. 
406 
vitreous. 
473 
Incomplete flower, part lacking 
Humus, formed by leaf decay . 
351 
in. 
203 
Hybrids. 
243 
Incomplete metamorphosis 
26 
Hydra, cell layers in ... 
160 
Increasing the food supply 
423 
described. 
160 
Incurrent siphon of clam 
191 
example of coelenterate 
160 
Indefinite annual growth 
265 
laboratory study of. 
164 
Indehiscent fruits, defined 
237 
Hydra-like animals, described . 
164 
Independent existence of moss 
summary of. 
167 
gametophyte 
330 
Hydrastis, source of ... 
297 
Indeterminate inflorescence 
216 
Hydrochloric acid in artificial 
India, dependence on rice 
. 
296 
gastric acid. 
413 
Indian, environment of . 
97 
Hydrogen, proportion of, in 
Indian pipe. 
290, 369 
plants and animals . 
13 
Indigestion. 
429 
Hydroids, described .... 
164 
causes of. 
429 
examples of ccelenterates . 
160 
disguised by alcohol 
430 
Hydrophytes, definition of . . 
370 
tablets for. 
430 
finely-divided leaves of sub¬ 
Indistinct ring, left by 1 
bud 
merged forms. 
370 
scales. 
264 
Hydrotropism, defined . . . 
286 
Inflorescence .... 
213 
in roots . 
862 
Influence of alcohol on develop- 
Hymenoptera, discussed . . . 
45 
ment of brain . 
481 
order of insects. 
29 
Influences affecting the growth 
Hyphse of bread mold 
323 
of plants .... 
286 
Hypocotyl, part of embryo . 
220 
Influenza. 
492, 493 
part to grow first .... 
220 
Infusoria. 
149 
use of, to embryo .... 
220 
Inhalent pores .... 
156 
Hypopharynx of grasshopper 
23 
Inhalers. 
484 
Inherited diseases ... 
487 
I 
Inner chamber of eye . . 
473 
Inner coat of pollen grain 
208 
Ice, a form of water .... 
10 
Inner ear. 
475 
use of, in caring for milk . 
314 
Inoculation 
258 
Ice cream, dangers from . 
316 
Inorganic foods. 
412 
Ichneumones, discussed . 
41 
Inorganic matter 
10 
enemy of Lepidoptera . . . 
41 
Insanity. 
487 
members of order Hymenop- 
Insect, group, divisions of 
. 
28 
tera. 
45 
pollination. 
210 
Imbecility. 487, 536 
Insecta . 
9 
