370 INDEX. 



PAGE 



Gravitation, experiments with regard to its effects on the direction of the radicle 



and germen ........ .... 124 



, its influence on the germinating parts of seeds . . . . 157 



, its effects upon the plumules of germinating seeds . . .167 



, its tendency to depress horizontal branches, how counteracted . 127 



occasions the deposition of woody matter on the under-side of 



branches to be greater than elsewhere 127 



, its effect on differently organized bodies 190 



on the direction of stems 300 



on melons ,318 



and light, their conflicting influences on the direction of leaves . 306 



Guernsey Lily, on its culture 236. 292 



1 effects of extremes of temperature on 239 



HEARTWOOD ............ 95 



Heat, its effect on the motion of sap ........ 90 



, degree of, necessary to put the sap in motion, depends on the previous 



excitement of the plant 90 



, excessive, in forcing-houses during the night, on its ill effects . .213 



Heaths, exotic, suggestion of a liquid manure for 213 



Horizontal branches 101.127 



Hot air 299 



Hotbeds, an account of some improvements in their construction . . . 298 



Hot-houses, with curvilinear iron roofs, advantages of 245 



1 upon the advantages and disadvantages of curvilinear iron roofs for 263 



heated by warm air ... 272 



Humidity . . . 226 



Hybrids, observations on ..... 25 1 



INSECTS, means of their destruction ..... . . 245 



_ by the application of hot water . .306 



Inverted shoots 107 



Irrigation of garden grounds, by means of tanks or ponds, on the advantages of 332 



Ivy . . 164 



, nature of its claspers, and their evasion of light . . . . . . 165 



, its capability of maintaining, by particular management, an independent 



form 288 



protects plants from cold . 288 



LAUBUS PERSEA 240 



Layering, a mode by which peach and nectarine trees may be propagated . . 274 



Layers, on facilitating the emission of roots from 195 



Leaves, different tubes which they contain 117 



, distinct offices of their surfaces . . . . . . . .97 



- derive not their first nutriment from the crude sap . . . . 115 

 , their mode of attachment 86 



