368 INTRODUCTION TO BOTANY 
Winged fruits and seeds, 170 
Winter buds, 94 
Winter spores of wheat rust, 254, 
255* 
Wood, coniferous, 108, 109* 
Wood, fuel value of, 108 
Wood, hard, 109, 110* 
Wood, physical properties of, *107- 
110 
Wood, structural advantages of, 107, 
108 
Wood, structure of, 62%, 63*, 65%, 
109%, 110* 
Wood, tracheids of, 109* 
Wood fibers, 64 
Wood sections, 65*, 109%, 110* 
Xerophytes, 28, 29%, 80*, 81*, 82, 83 
Yeast, 246* 
Zoospores, 227* 
Zygomorphic flowers, 128*, 129 
Zygospore, 224*, 225, 228 
