SUBJECT INDEX 



695 



Vapor pressure, 160, 193, 194 

 of atmosphere, I94-I95> 198-200 

 of intercellular spaces, 1 94-195, 



198-200, 207-209 

 relation to diffusion pressure defi- 

 cit, 207 

 Vapor pressure deficit, 193, 194 

 Vapor pressure gradient, 193, 199, 



200, 205-209 

 Vapor pressure theory of osmosis, 98- 



99 

 Vascular ra^'s, 228, 485, 559 

 Vegetative growth, correlation with 



reproduction, 617-619 

 Velocity of chemical reactions in gels, 



55 

 Vernalization, 612 

 Vessels, 219, 221, 222, 224-226, 227, 



229, 271, 482, 650 

 Vessel segment, 226 

 Viscosity, 



of cytoplasm, 73-74 

 of sols, 44 

 "Vital" theories of movement of wa- 

 ter, 229-231 

 Vitamin B^, 582 



Wall pressure, 97, 145-151, 153, 



293, 295 

 Water, 



adsorption of, 30 



as a membrane, 128-129 



as a solvent, 7 



cohesion (cohesive force) of, 24, 



233-234, 236-238 

 permeability of cytoplasmic mem- 

 branes to, 122 

 pH of, 16, 18 



redistribution in plants, 295-298 

 tension in, 149, 234-235, 237-241 

 Water, efifect of, 



on germination, 630 

 on growth, 607-609, 643-644 

 Water absorbing power of cells, 

 148 



Water content of leaves, 294 

 daily variations in, 289-291 

 Water content of leaves, effect of 

 on photosynthesis, 357-359 

 on starch-sugar equilibrium, 387 

 on stomatal opening, 186-187 

 Water content of soils, 256 

 Water content of soils, effect of, 

 on absorption of water, 280-281 

 on anthocyanin synthesis, 384 

 on transpiration, 201, 210, 358 

 Water content of tree trunks, 233 

 Water deficit in plants, 289-290, 292, 



293, 296-298, 301 

 Water relations of the soil, 251-255 

 Water retaining capacity of soils, 256- 



257 



Water stomates, 170 



Water table, 251-252 



Waxes, 396 



Wilting, 



incipient, 186, 206, 288-289, 291 

 permanent, 258-259, 288, 294- 



295, 297 

 temporary (transient), 287-289, 

 291, 294 



Wilting percentage (wilting coeffi- 

 cient), 257-259, 261-262, 277 



Wind, effect on transpiration, 200- 

 201 



Winter-killing, 211, 591 



Wood fibers, 227, 228 



Wood parenchyma, 222, 226-228, 

 561 



Wood rays, 221, 222, 223, 225 



Wound hormones, 582 



Xanthophylls, 315, 316, 317, 385 

 X-rays, effect on growth, 600 

 Xylans, 375 



Xylem, 157, 216, 217-229, 270, 481 

 Xylem, primary, 270, 482, 560 

 Xylem, secondary, 217, 220, 224, 



272, 560, 561 

 Xylem exudation, 171, 231-232 

 Xylem fibers, 227 



