INDEX. 363 



u. 



Unisexual plants, effects of temperature on, 82 



V. 

 Valleys, superior general warmness of, 139— their liability to sudden 



cold, 189. 

 Vaporous impurities, 152. 

 Varieties not absolutely permanent through propagation by seeds, 



296 — means of fixing them, 297 — contamination of, 302. 

 Vegetation, relative advancement of, in stocks and scions, 234 — in 



forcing houses, mode of resting itj 330. 

 Veins of leaves consist of two systems, 37' — their structure, 87. 

 Ventilation, 150 — under some circumstances injurious,. 151 — circum- 



etances which render it necessary, 152. 

 Vine, its cultivation in the open air in England, cause of the general 



■want of success in, 99 — great power of its ascending sap, 47 — • 



preventive against its bleeding, 245 

 Vine borders, their preparation, 119. 

 Vines, a cause of their not setting, 106. 

 Vital forces of vegetation, 40 — principle is stimulated by heat, 9, 107 



— principle in seeds, 175 — force in plants decomposes water, 40 



— functions of plants, 125. 

 Vitality in seeds, causes of its destruction, 111. 



W. 



Walls, effect of blackening, 188 — importance of, with regard to 

 shelter, 181. 



Walnut, propagation of, by budding, 233. 



Water, a vehicle by which oxygen is supplied during the process of 

 germination, 9 — in variouB respects conducive to germination, 9 

 — enters into the composition of the food of plants, 18 — pure, 

 cannot solely support vegetation for a long period, 18 — is de- 

 composed by the vital action of plants, 18, 41 — proportions of, 

 in certain vegetable secretions, 96 — an excessive supply of, re- 

 tards the ripening of fruits, 76 — its decomposition or dissipation 

 by fruits, 76 — in a tepid state applied to roots, 109 — in which 

 aquatics are grown, necessity of regulating it to a due degree of 

 temperature, 109 — in the soil, should be diminished when succu- 

 lent fruit is ripening, 116 — stagnation of, 275 — absorption of, 



