44 



INDEX 



References are to pages 



Winter visitants, examples of 141 

 Wistaria, member of the pulse 



family 329 



Witch-hazel, explosive fruit of 312 

 Wood, example of organic mat- 

 ter 10 



formation of 290 



of spruce (fig.) 290 



sections of (fig.) 290 



Woodchucks, young (fig) • • 157 

 Wooded area, under govern- 

 ment control 387 



Woodpeckers, at suet station 148 



(downy) permanent residents . 141 



food of 27, 31 



holes made by (fig.) .... 27 



Wood-pulp, source of ... . 384 



Woody stem, sections of (fig.) 289 



structure of 287 



use of elements in 290 



Woody twig, buds of ... . 287 



Wool, source of 155 



indirect product of plants . . 401 

 Woolly aphis, member of He- 



miptera (fig.) 24, 25 



Work, of the yeast plant . . . 354 



of bean leaf 275 



Workers (bees) 35 



Worm, in the apple (fig.) ... 18 



planarian (fig.) 77 



Worm-like animals, classified 6 



Worm group, discussed ... 76 



summary of 84 



Worms, classified 6 



Wort, formation of 355 



Wren, a useful bird 145 



food of 31 



X-ray photograph, of appen- 

 dix and part of large intes- 

 tine (fig.) . 169 



of Easter lily (fig.) .... 327 



of elbow (fig.) 185 



of hand of adult (fig.) .... 186 



of child (fig.) 186 



of human stomach (fig.) . . . 168 



Xylem, conductor of water . . 290 



in fibrovascular bundle of corn 280 



position in vascular bundle . . 269 



relation to cambium .... 287 



Xerophytes 



396 



Year's growth of twig, how 



told 289 



Yeast, in bread making . . ' . 179 

 plant, described (fig.) . . . 354, 355 



enzyme of 354 



use of 355 



reproduction of 3 



Yellow fever, carried by mos- 

 quito 42, 239 



caused by protozoa . . .47, 234 

 Yellow pine, value of ... . 385 

 Yellow swallowtail (fig.) . . 33 

 Yellow warbler, nest of (fig.) . 142 



Yolk, of fish eggs 109 



sac on young fish (fig.) • • . HI 

 Youth, a period of life .... 163 



Zeppelins, use of hydrogen gas 



for 8 



Zygospore, advantages of . . 341 



Zygote of spirogyra .... 341 



Zymase, work of 179 



IMPORT U8HARY 



% C State CWIejfe 



