INDEX. 863 



u. 



Unisexual plants, effects of temperature on, 82 



V. 

 Valleys, superior general warmness o^ 139 — ^their liability to sudden 



cold, 139. 

 Vaporous impurities, 152. 

 Varieties not absolutely permanent through propagation by seeds, 



296 — njeans of fixing tliem, 297 — contamination of, 302. 

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



forcing houses, mode of resting it, 330. 

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

 Ventilation, 150 — under some oiroumstanoes injurious, 151 — eircum- 



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 — ^foree in plants decomposes water, 40 



— functions of plants, 125. 

 Vitality in seeds, causes of its destruction. 111. 



W. 



Walls, effect of blackening, 138 — ^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 various respects conducive to germination, 9 

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

 cannot solely support veijetation 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 ripeuiug 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 o^ 



