viii CONTENTS 



XXX. SOUND 294 



XXXI. VOCAL CORDS AND THE EARS 300 



XXXII. THE SOIL 305 



XXXIII. How TO CARE FOR SOIL 321 



XXXIV. How PLANTS GROW 335 



XXXV. How PLANTS ARE PROPAGATED 352 



XXXVI. USE OF PLANTS TO MAN 361 



XXXVII. Low FORMS OF PLANT LIFE 368 



XXXVIII. PLANT DISEASES AND PESTS 373 



XXXIX. THE ANIMAL SERIES 381 



XL. ANIMALS AS DISEASE CARRIERS 396 



XLI. MAN'S PLACE IN NATURE 404 



XLII. THE EARTH AND ITS NEIGHBORS 407 



APPENDIX The Metric System 415 



GLOSSARY 419 



SUGGESTIONS TO TEACHERS 425 



INDEX 429 



