604' 



INDEX 



Willow family, 473. 



Wilt Disease, 378. 



Wind, as an ecological factor, 502. 



Wing, of corolla, 24, 23*. 



Witches' Brooms, 377. 



Wood fiber, 129, 130, 130*. 



Xylem, 130, 130*; of roots, 146, 149, 

 146*, 149*; of stems, 188, 190 *. 



Yeasts, 377. 



Zooglea stage of Bacteria, 342, 343*. 



Zoospores, 302. 



Xanthophyll, 285. Zygospore, 302. 



Xenia, 51, 51*. Zygote, 302. 



Xerophytic societies, 509; kinds, 510. Zymase, 94, 284. 



